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官方真题Official4托福阅读Passage1原文文本+题目+答案解析（原TPO）

官方真题Official4托福阅读Passage1原文文本+题目+答案解析(原TPO)现在大家在进行托福备考时官方真题Official托福模考软件相信是大家用的最多的工具了，对于托福成绩的提升是非常有帮助的。

托福听力可以说是整个托福考试当中比较重要的一个部分，如何利用现有资料官方真题Official模考软件来提升大家的托福成绩呢?今天小编在这里整理了官方真题Official4托福阅读Passage1原文文本+题目+答案解析来分享给大家，希望对大家托福听力备考有帮助。

官方真题Official4托福阅读Passage1原文文本Deer Populations of the Puget SoundTwo species of deer have been prevalent in the Puget Sound area of Washington State in the Pacific Northwest of the United States. The black-tailed deer, a lowland, west-side cousin of the mule deer of eastern Washington, is now the most common. The other species, the Columbian white-tailed deer, in earlier times was common in the open prairie country; it is now restricted to the low, marshy islands and flood plains along the lower Columbia River.Nearly any kind of plant of the forest understory can be part of a deer's diet. Where the forest inhibits the growth of grass and other meadow plants, the black-tailed deer browses on huckleberry, salal, dogwood, and almost any other shrub or herb. But this is fair-weather feeding. What keeps the black-tailed deer alive in the harsher seasons of plant decay and dormancy? One compensationfor not hibernating is the built-in urge to migrate. Deer may move from high-elevation browse areas in summer down to the lowland areas in late fall. Even with snow on the ground, the high bushy understory is exposed; also snow and wind bring down leafy branches of cedar, hemlock, red alder, andother arboreal fodder.The numbers of deer have fluctuated markedly since the entry of Europeans into Puget Sound country. The early explorers and settlers told of abundant deer in the early 1800s and yet almost in the same breath bemoaned the lack of this succulent game animal. Famous explorers of the north American frontier, Lewis and Clark arrived at the mouth of the Columbia River on November 14, 1805, in nearly starved circumstances. They had experienced great difficulty finding game west of the Rockies and not until the second of December did they kill their first elk. T o keep 40 people alive that winter, they consumed approximately 150 elk and 20 deer. And when game moved out of the lowlands in early spring, the expedition decided to return east rather than face possible starvation. Later on in the early years of the nineteenth century, when Fort Vancouver became the headquarters of the Hudson's Bay Company, deer populations continued to fluctuate. David Douglas, Scottish botanical explorer of the 1830s, found a disturbing change in the animal life around the fort during the period between his first visit in 1825 and his final contact with the fort in 1832. A recent Douglas biographer states:" The deer which once picturesquely dotted the meadows around the fort were gone [in 1832], hunted to extermination in order to protect the crops.Reduction in numbers of game should have boded ill for their survival in later times. A worsening of the plight of deer was to be expected as settlers encroached on the land, logging, burning, and clearing, eventually replacing a wilderness landscape with roads, cities, towns, and factories. No doubt the numbers of deer declined still further. Recall the fate of the Columbian white-tailed deer, now in a protected status. But forthe black-tailed deer, human pressure has had just the opposite effect. Wildlife zoologist Helmut Buechner(1953), in reviewing the nature of biotic changes in Washington through recorded time, says that "since the early 1940s, the state has had more deer than at any other time in its history, the winter population fluctuating around approximately 320,000 deer (mule and black-tailed deer), which will yield about 65,000 of either sex and any age annually for an indefinite period."The causes of this population rebound are consequences of other human actions. First, the major predators of deer—wolves, cougar, and lynx—have been greatly reduced in numbers. Second, conservation has been insured by limiting times for and types of hunting. But the most profoundreason for the restoration of high population numbers has been the fate of the forests. Great tracts of lowland country deforested by logging, fire, or both have become ideal feeding grounds of deer.In addition to finding an increase of suitable browse, like huckleberry and vine maple, Arthur Einarsen, longtime game biologist in the Pacific Northwest, found quality of browse in the open areas to be substantially more nutritive. The protein content of shade-grown vegetation, for example, was much lower than that for plants grown in clearings.官方真题Official4托福阅读Passage1题目Question 1 of 14According to paragraph 1, which of the following is true of the white-tailed deer of Puget Sound?A. It is native to lowlands and marshes.B. It is more closely related to the mule deer of eastern Washington than to other types of deer.C. It has replaced the black-tailed deer in the open prairie.D. It no longer lives in a particular type of habitat that it once occupied.Question 2 of 14It can be inferred from the discussion in paragraph 2 that winter conditionsA. cause some deer to hibernateB. make food unavailable in the highlands for deerC. make it easier for deer to locate understory plantsD. prevent deer from migrating during the winterQuestion 3 of 14The word "inhibits " in the passage is closest in meaning toA. consists ofB. combinesC. restrictsD. establishesQuestion 4 of 14The phrase "in the same breath " in the passage is closest in meaning toA. impatientlyB. humorouslyC. continuouslyD. immediatelyQuestion 5 of 14The author tells the story of the explorers Lewis and Clark in paragraph 3 in order to illustrate which of the following points?A. The number of deer within the Puget Sound region has varied over time.B. Most of the explorers who came to the Puget Sound area were primarily interested in hunting game.C. There was more game for hunting in the East of the UnitedStates than in the West.D. Individual explorers were not as successful at locating games as were the trading companies.Question 6 of 14According to paragraph 3, how had Fort Vancouver changed by the time David Douglas returned in 1832?A. The fort had become the headquarters for the Hudson's Bay Company.B. Deer had begun populating the meadows around the fort.C. Deer populations near the fort had been destroyed.D. Crop yields in the area around the fort had decreased.Question 7 of 14Why does the author ask readers to recall “the fate of the Columbian white-tailed deer ” in the discussion of changes in the wilderness landscape?A. To provide support for the idea that habitat destruction would lead to population declineB. To compare how two species of deer caused biotic changes in the wilderness environmentC. To provide an example of a species of deer that has successfully adapted to human settlementD. To argue that some deer species must be given a protected statusQuestion 8 of 14The phrase “indefinite period ” in the passage is closest in meaning to periodA. whose end has not been determinedB. that does not begin when expectedC. that lasts only brieflyD. whose importance remains unknownQuestion 9 of 14Which of the following statements about deer populations is supported by the information in paragraph 4?A. Deer populations reached their highest point during the 1940s and then began to decline.B. The activities of settlers contributed in unexpected ways to the growth of some deer populations in later times.C. The cleaning of wilderness land for construction caused biotic changes from which the black-tailed deer population has never recovered.D. Since the 1940s the winter populations of deer have fluctuated more than the summer populations have.Question 10 of 14The word “rebound ” in the passage is closest in meaning toA. declineB. recoveryC. exchangeD. movementQuestion 11 of 14Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.A. Arthur Einarsen’s longtime family with the Pacif ic Northwest helped him discover areas where deer had an increase in suitable browse.B. Arthur Einarsen found that deforested feeding grounds provided deer with more and better food.C. Biologist like Einarsen believe it is important to findadditional open areas with suitable browse for deer to inhabit.D. According to Einarsen, huckleberry and vine maple are examples of vegetation that may someday improve the nutrition of deer in the open areas of the Pacific Northwest.Question 12 of 14Which of the following is NOT mentioned in paragraph 5 as a factor that has increased deer populations?A. A reduction in the number of predatorsB. Restrictions on huntingC. The effects of logging and fireD. Laws that protected feeding grounds of deerQuestion 13 of 14Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit?There food is available and accessible throughout the winter..Question 14 of 14Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Deer in the Puget Sound area eat a wide variety of foods and migrate seasonally to find food.A.The balance of deer species in the Puget Sound region has changed over time, with the Columbian white-tailed deer now outnumbering other types of deer.B.Deer populations naturally fluctuate, but early settlers in the Puget Sound environment caused an overall decline in thedeer populations of the areas at that time.C.In the long term, black-tailed deer in the Puget Sound area have benefitted from human activities through the elimination of their natural predators, and more and better food in deforested areas.D.Because Puget Sound deer migrate, it was and still remains difficult to determine accurately how many deer are living at any one time in the western United States.E.Although it was believed that human settlement of the American West would cause the total number of deer to decrease permanently, the opposite has occurred for certain types of deer.F.Wildlife biologists have long been concerned that the loss of forests may create nutritional deficiencies for deer.官方真题Official4托福阅读Passage1解析Question 1 of 14正确答案：D题目解析：以White-tailed deer做关键词定位至最后一句：The other species, the Columbian white-tailed deer, in earlier times was common in the open prairie country; it is now restricted to the low, marshy islands and flood plains along the lower Columbia River.说白尾鹿过去是什么什么地方的，现在是什么什么地方的，也就是它们的生活环境发生了变化，所以D不再在原来的地方生活正确。

视听说教程第三册听力原文

Unit 1 Lesson 1VideoHome ListeningA conservation group says 163 newly discovered species of plantsand animals in the Greater Mekong region of Southeast Asiawhere the Mekong River 1) flows are at risk of extinction becauseof rising global temperatures.Some of the most 2) unusual animalsincluded a frog with fangs in Thailand that eats birds and a leopard-spottedgecko found on an island in Vietnam. But in a report 3) released in Bangkokon Friday, the WWF says that temperatures in the region are 4) expected torise by as much as four degrees Celsius in the next 60 years and that couldthreaten their existence.The WWF says rare and endangered species are at the greatest 5) risk from climate change, because rising temperatures could affect food 6) supplies or cause weather problems that damage habitats. The newly discovered species that live at the tops of mountains only or low-lying islands only, like this Cat Ba gecko that was just found are 7) especially vulnerable to climate-change impacts because of their restricted habitats. More than 1,000 new species have been discovered in the Greater Mekong region in the past 8) decade.Changes to wildlife in the Mekong area could also affect many of the 60 million people who depend on the river for their livelihoods. Of all the region‟s the WWF works in, the Mekong region 9) probably has the closest link between its resource and human livelihood than any other region in the world.The WWF report comes just days ahead of a major United Nations meeting in Bangkok on climate change. The Bangkok meeting will 10) try to narrow down a framework agreement on global emission targets to be negotiated at the end of this year.Unit 2Lesson 1AudioScriptWhen it comes to intelligence, there has always been one fundamental question: Is intelligence a function of nature? Is it simply encoded in a child‟s genes? Or is it a function of nurture? Is it more about the environment that a child grows up in?On the one hand, if we take two people at random from the crowd, it is very likely that their degrees of intelligence will be completely different. However, if we take two identical twins, chances are that they will be as intelligent as each other. Therefore, a conclusion can be drawn thatintelligence is to some extent something we are born with. On the other hand, though, if we put identical twins in different environments, we would find differences in their intelligence several years later, which indicates that environment does play a crucial role in people‟s intelligence.Recently, data has clearly indicated that nurture is indeed more than 50% of the equation. That is good news for educators, but even better news for society as a whole.Fortunately, President Obama has come out in strong support of early childhood education, particularly for those children most at risk of school failure. Investing in quality pre-school opportunities clearly helps give children from poverty-stricken areas the chance at a stronger start in school and in life.If we are serious about helping our children succeed in school, if we are truly interested in “Leaving No Child Behind,” we will take a hard look at t his compelling data and begin investing greater sums at the early childhood level.VideoScriptEinstein‟s destiny as a great physicist was not obvious. As a child, his passion was music, not physics.“I often think in music. I live my daydreams in music. If I were not a physicist, I would probably be a musician.”But Einstein‟s life changed when he was given a book on geometry. The universe could be tamed through numbers. His life‟s work would be to control the music of the universe.During his life, Einstein changed our concept of space and time forever. He harnessed energy, mass and the speed of light in the most famous equation all time – E equals MC‟ square.What made Einstein‟s brain so exceptional? Dr. Jim Al-Khalili, like Einstein, is a physicist and is obsessed by the work of his hero. Brain specialist，Mark Lythgoe hunts for secrets of creativity inside the human mind.“My name is Dr. Jim Al-Khalili I believe Einstein‟s genius came from his imagination, and no man or no machine can measure that. Am I right?”“M y name is Dr. Mark Lythgoe and I believe that Einstein‟s genius comes from nerve cells, which can be analyzed. We can find out what made Einstein a genius. Am I right?”So which view is correct? To solve the riddle of Einstein‟s genius, Mark and Jim would have to journey to America to hunt down and examine Einstein‟s disembodied brain. Nature or nurture? Biology or training? Are geniuses born or are they made? Neurophysiologist Dr. Mark Lythgoe is a keen climber and finds parallels between his hobby and his profession.“N ow, there are two scenarios for how the brain works. The first scenario is the brain is like a muscle. Now I‟ve trained to develop the stamina in my muscle, hopefully then I can hold on to this hole for a period of time. The second is that the brain is like a skeleton and it doesn‟t matter how much I‟ve trained, I‟m never, ever going to be able to reach that hole right up there. “Now, in Einstein‟s day they believed that the brain was like a skeleton that had natural limits, but that view is changing today. Instead, it is now understood that more and more parts of the brain behave like a muscle. They can expand with use. Then, if all of our brains are like muscles, could it be that we all have the ability to become Einstein?”Lesson 2AudioAlbert Einstein was a German-born physicist, although most people probably know him as the most intelligent person who ever lived. His name has become part of many languages when we want to say someone is a genius, as in the phr ase, “She‟s a real Einstein”. He must have been pretty brainy to discover the Theory of Relativity and the equation e=mc2.In 1999, Time Magazine named Einstein as the Person of the Century. No one could have guessed this would happen when he was in school. He was extremely interested in science but hated the system of learning things by rote memory. He said it destroyed learning and creativity. He had already done many experiments but failed the entrance exams to a technical college.He didn‟t let this s etback stop him. When he was 16, he performed his famous experiment of imagining traveling alongside a beam of light. He eventually graduated from university, in 1900, with a degree in physics.Twelve years later he was a university professor and in 1921, he won the Nobel Prize for Physics. He went on to publish over 300 scientific papers.Einstein is the only scientist to become a cult figure, a household name and part of everyday culture. He once joked that when people stopped him in the street, he alway s replied, “Pardon me, sorry! Always I am mistaken for Professor Einstein.” Today, he is seen as the typical mad, absent-minded professor, who just happened to change our world.VideoScriptSo Einstein‟s brain has given up some of its secrets to Mark and Jim. In the battle of biology versus ideas, Jim and Mark have each scored points. Seemingly, Einstein was born with overlaps in his brain. These overlaps may have meant maths and spatial thinking were more intuitive to him. Thinking like a child let him see the world in a unique way. And his unique, perhaps autistic, level of concentration, forced his brain to expand like a muscle. Extra glial cells were needed to cope with the extra demand, possibly helping make the maths area in the brain more than 15% wider than normal. All these effects united to give Einstein a mind unlike any other, perhaps the greatest mind in history. In the future, could we preserve a genius like Einstein in something better than the jar? Imagine a brave new world, where a genius‟brain could be copied onto silicon using microscopic robots called nanobots. This is the vision of the futurologist Ray Kurzweil.“I think by the 2020s or the late 2020s, we will have completely reverse engineered the brain and understand how all the diff erent regions work. It‟ll take us longer to be able to scan the entire brain and get capture of every detail of someone‟s personality. The blood vessels of the brain go everywhere, and so if we send billions of nanobots through the capillaries of the brain, they can scan everything in the brain of a specific person at very high resolution. Then you could create a machine, a non-biological entity, that would simulate a specific person‟s brain and that simulation will act just like that person, and if you the n talk to that simulation, you‟d be convinced that it was that person.”“I am little worried about whether I‟m talking to the real Ray or he‟s at home having a cup of tea.”“Well, I worry about that too. Once we understand the basic principles of operatio n of how the brain works, we can take a brain-like system and expose it to a complicated problem and the system will learn on its own. It can actually do it thousands maybe eventually millions of times faster than a real human brain and actually develop skills that are far greater than a human being isSo a future Einstein could be put on a computer, literally a ghost in the machine.“Do you believe that, you know, just by looking at that, genius is– or genius is something else for you?It‟s a k ey moment. Has Mark won Jim round?“Day by day, I‟ve been changing my views. I‟ve been–I started off feeling that Einstein‟s ideas have gone forever. What he thought of, what he‟s capable of imagining were something of the past. I‟m not so sure now. I fe el somehow there are still, maybe, possibly, some secrets locked inside in this jar.”Home ListeningMost people know that Albert Einstein was a famous scientist who came up with the formula e=mc2. But do you know other facts about this 1) genius?When Einstein died in 1955, his body was cremated and his ashes 2) scattered according to his wishes. However, before his body was cremated, Thomas Harvey at Princeton Hospital 3) conducted an autopsy in which he removed Einstein‟s brain. Rather than putting the brain back in the body, Harvey decided to keep it for study. Harvey did not have 4) permission to keep Einstein‟s brain, but days later, he 5) convinced Einstein‟s son that it would help science. Shortly thereafter, Harvey was fired from his position at Princeton because he refused to give up Einstein‟s brain. For the next four 6) decades, Harvey k ept Einstein‟s chopped-up brain in two mason jars with him as he moved around the country.Einstein‟s mother, Pauline, was an 7) accomplished pianist and wanted her son to love music too, so she started him on violin lessons when he was six years old. Unfortunately, at first, Einstein hated playing the violin. 8) He would much rather build houses of cards, which he was really good at, or do just about anything else. When Einstein was 13-years old, he suddenly changed his mind about the violin when he heard the music of Mozart. 9) With a new passion for playing, Einstein continued to play the violin until the last few years of his life.Part of Einstein‟s charm was his disheveled look. In addition to his uncombed hair, one of Einstein‟s peculiar habits was to never wear socks. 10) Whether it was while out sailing or at a formal dinner at the White House, Einstein went without socks everywhere. To Einstein, socks were a pain because they often would get holes in them. Plus, why wear both socks and shoes when one of them would do just fine?Unit 3Lesson 1AudioScriptMcDonald‟s Corporation (MCD) is one of the leading fast-food restaurant chains in the world, touching the lives of people every day. As the world‟s largest chain of restaurants, it primarily sells hamburgers, chicken, french fries, milkshakes, soft drinks, etc.The business began in 1940, with a restaurant opened by brothers Dick and Mac McDonald. Initially, they just owned a hotdog stand. But after establishing the restaurant they served around 25 items, which were mostly barbecued. It became a popular and profitable teen hangout.Their introduction of the “Speed Service System” in 1948 established the principles of the modern fast-food restaurant. The present corporation dates its founding to the opening of a franchised restaurant by Ray Kroc on April 15, 1955.In effect, Kroc opened his first and the overall ninth restaurant in Chicago, Illinois, and gave birth to McDonald‟s Corporation. In 1958, the restaurant chain sold its 100 millionth hamburger. In 1960, Kroc renamed his company as “McDonald‟s Corporation”. In 1961, Kroc convinced the McDonald brothers to sell the business rights to him in the company. Thus he purchased the brothers‟ equity for a sum of $2.7million and led to its worldwide expansion.As McDonald‟s expands successfully into many international markets, the company became a symbol of globalization and the spread of the American way of life. Its prominence also made it a frequent subject of public debates about obesity, corporate ethics and consumer responsibility. VideoScriptTanya: It‟s the fast food chain with the iconic golden arches that have been spotted all over the world. Yes, we are talking about McDonald‟s. But did you know McDonald‟s, year after year, is voted one of the best places to work? We‟re looking today at this all-American company and what we can learn from its success. We‟re joined by Paul Facella, author of the book, Everything I Know About Business, I Learned At McDonald’s: The Seven Leadership Principles That Drive Breakout Success. Paul was a former McDonald‟s executive who has the behind-the-scenes story on the world‟s most successful restaurant organization. Hi there, Paul. Thanks for joining us. Paul: Thank you, Tanya. Nice to be here.Tanya: Now, while you no longer work for McDonald‟s, I understand that the company has had a huge impact on your life. Tell us why you decided to write a book on business lessons that you learned from a fast food chain.Paul: Sure. Well, not only myself but literally hundreds of thousands of people that went to the McDonald‟s system and were guided by a lot of the principles. When I left McDonald‟s, I went into consulting and, and one of the surprises I had was many of the organizations, both large and small, was the fact that some of the basic principles, some of the foundations that good organizations need to be successful, weren‟t there. And I was constantly being asked about, “Well, tell me how you did in McDonald‟s”. And my thinking was, “Gee, I‟ll write a book about it and help my client base and I‟ll be able to help them move forward with it.” So that was the thinking behind it.Tanya: Well, we‟re gonna get into some of those secrets of success. I wanna start by asking you, you know, obviously a lot of people know McDonald‟s for their burgers and Big Macs. But, I‟m sure a lot people will be surprised to know that it has one of the highest corporate employee retention rates of any company, I mean people assume, fast food chain, people just want to get in and get out. What makes McDonald‟s so successful?Paul:I think, I think there‟s a number of factors, but I think the retention piece is about McDonald‟s, when you work, there it‟s really about a meritocracy. It is about advancement that is based on achievement. And from the first crew person moving in all the way up to store manager, all the way up to the present CEO, Jim Skinner, who was a crew person 35 years ago and moved into, after 35 years, moved into the CEO ranks. So it‟s always been a progression of opportunity for people, and I think that's one of the great things that keeps folks there. Every CEO has gone through the ranks.Tanya: Is there any crossover from those who work on the server side to the executive side, or you have to go back to school for that?Paul: Oh, no, all the time, I mean, I started as a 16-year-old crew person. Mike Quinlan, who‟s a CEO for 14 years started in the mail room, so there‟s plenty of crossover.Lesson 2AudioScriptSince setting up the first McDonald‟s in China, the Western restaurant chain has been expanding steadily and successfully. So far, other than the home market–the United States–China is the No. 1 growth market for McDona ld‟s, with over 1000 restaurants and over 60,000 employees.China also represents one third of all capital expenditures in the Asia-Pacific, Middle East and Africa region, where the fast-food giant is in 37 markets. According to Skinner, vice-chairman and CEO of this world‟s largest fast-food company, “We‟ve been steadily growing with China for the past 20 years and are very excited for what the future holds,” he says.In 1990, McDonald‟s chose Shenzhen, a pioneer Special Economic Zone in Guangdong province bordering Hong Kong, to open its first 500-seat store in the developing market. McDonald‟s quickly won over the local consumers, due to its many attractions like its Ronald McDonald clown, Golden Arches or the yellow “M” logo, Big Mac, the smiling attendants and the quick service. The success of the Shenzhen outlet prompted McDonald‟s to expand its chain nationwide. And McDonald‟s has not stopped from aggressively increasing the number of its outlets in China. The mainland‟s fast-food market is growing at a rate of16 percent per year. “We are going to continue our growth at a faster rate in China. China is a huge market with great opportunities for businesses around the world, and it's no different for McDonald‟s,” Skinner adds.VideoScriptT anya: And in your book, you‟ve broken down some of the keys, the fundamental keys of McDonald‟s success, in terms that can be applied to other companies. So, let‟s go through these one by one. The first you say is honesty and integrity, and this obviously comes at a time when so many people have lost trust in Wall Street. How can we apply this?Paul: Yeah, I think, it‟s, well, honesty and integrity started very early on with Ray Kroc who started the McDonald‟s system in 1955, and back then franchise s were just starting to proliferate, and there were not a lot of laws about how they would conduct businesses. And one of the things was done, sadly, was that many of those franchisors would take commissions back from suppliers that supplied the franchisees product. From the beginning, that's now how we‟re gonna do businesses. We‟re gonna have integrity, we‟re gonna be honest with our franchisees, I wanna the franchisees to make the first dollar, I‟ll make the second dollar, and that kind of got into the DNA very early. And to this day, there is a wonderful relationship of integrity and honesty with our relationships with our operators, with our vendors.Tanya: And I would imagine that motivates everybody because you feel like if you do well, you will get rewarded.Paul:That‟s correct. Absolutely, no question about that. How important everybody working together as a team is!Tanya: Right, and another secret to McDonalds‟ success, I understand, is relationships, and the company apparently promotes the idea that relationships are sort of the secret sauce, as, if you will, and everyone who works for the company is a part of an extended family, is that right?Paul: The Mcfamily!Tanya: Yeah.Paul: It's a great safe way from honesty and integrity. If you start with the foundation of honesty [and] integrity, it goes right into relationships. And Fred Turner, who is still to this day, 54 years later, is active, was actually the one that coined the phrase “the three-legged stool”. What it really meant was, that there were three legs in our relationship: the franchisees, the suppliers and the company people. And all of us pulling together, and working together as a team and the synergy of that team, is how it will be successful. And if you think about that, you know how important that is, that you really don‟t want to let your team members down and you want them to be successful. Tanya: Sure, and every leg of the stool is only as strong as the other leg, right?Paul: Absolutely.Tanya: And another secret is the idea of standards. One of the McDonalds‟ mottos, apparently, is never be satisfied? [Yes.] Tell us about the company‟s no excuses working environment.Paul: Yeah, well, standards are very important and you know is – in order to have a standard, you have that measurement, and if it‟s worth doing, it‟s worth measuring. And every time you measure something, performance improves because people have a guideline –they know where they‟re going, and that, that‟s actually part of even the people side of that. The meritocracy wasn‟t based on anything, but clear metrics on how you advance through the ranks on that. But it was never satisfied, we always felt we could do it harder, quicker, faster. And that stayed one step ahead of the competition and kept our franchisees the best in the system.Home ListeningInternational business is a term used to collectively describe all commercial transactions (private and governmental, sales, investments, logistics,and transportation) that take place between two or more nations. Usually, private companies 1) undertake such transactions for profit; governments for profit and for political reasons. It refers to all business activities which involve cross 2) border transactions of goods, services and resources between two or more nations. Transaction of economic resources include capital, skills, people, etc. for international production of physical goods, and services such as finance, banking, 3) insurance, construction, etc.The increase in international business and in foreign 4) investment has created a need for executives with knowledge of foreign languages and skills in cross-cultural communication. Americans, however, have not been well trained in either area and, consequently, have not enjoyed the same level of success in 5) negotiation in an international arena as their foreign counterparts. Negotiating is the process of communicating back and forth for the purpose of reaching an agreement. It involves persuasion and compromise, but in order to 6) participate in either one, the negotiators must understand the ways in which people are persuaded and how compromise is reached within the culture of the negotiation.In studies of American negotiators abroad, several traits have been 7) identified that undermine the negotiator‟s position, two of which, in particular, are directness and 8) impatience. Furthermore, American negotiators often insist on realizing short-term goals. Foreign negotiators, on the other hand, may value the relationship established between negotiators and may be willing to invest time in it for long-term benefits. 9) In order to solidify the relationship, they may chooseindirect interactions without regard for the time involved in getting to know the other negotiator. Clearly, perceptions and differences in values affect the outcomes of negotiations and the success of negotiators. 10) For Americans to play a more effective role in international business negotiations, they must put forth more effort to improve cross-cultural understanding.Unit 4Lesson1AudioScriptA leading US scientist has predicted that computers will be as intelligent as humans by 2029. Futurologist Dr Ray Kurzweil told the American Association for the Advancement of Science that in the near future, machine intelligence will overtake the power of the human brain. He said that within two decades computers will be able to think quicker than humans. Dr Kurzweil painted a picture of us having tiny robots called nanobots implanted in our brain to boost our intelligence and health. He told reporters that these microscopic nanobots would work with our brains to make us think faster and give us more powerful memories. Kurzweil explained that we are already “a human machine civilization” and that the upcoming technology “will be a further extension of that.”Dr Kurzweil was one of 18 top intellectuals asked by the US National Academy of Engineering to identify our greatest technological challenges. Other experts included Google founder Larry Page and the human genome pioneer Dr Craig Venter. Kurzweil has a very impressive background in science and innovation. He was an innovator in various fields of computing, including the technology behind CDs. He also pioneered automatic speech recognition by machines. He predicts the pace of new inventions will increase greatly from now, saying: “…the next half century will see 32 times more technical progress than the past half century.” This means scenes from science fiction movies, like Blade Runner, The Terminator and I Robot, will become more and more a part of our everyday lives.VideoScriptSurrogates today are more like Gina Scanlon and Jennifer (again, first name only), both from the Pittsburgh area.Scanlon, 42 years old, is a portrait painter and mother of three. She delivered twins as a surrogate two years ago. And now, in part because her husband Brian needs expensive surgery, Scanlon is pregnant again.In contrast, this is Jennifer‟s first try as a surrogate. She‟s a 36-year-old stay-at-home mother of two.Jennifer: Being a mother, I can‟t imagine life without my children and so you know. It really came to the fact that I would really like to help another couple have a child that they otherwise could not.Anchor: What about you Gina? What do you think is inside of you that said, …I want to be a surrogate‟?Gina: I love being pregnant. It‟s a great experience. And having met friends and family whoexperienced infertility, their choices are limited. I felt that I wanted to do this for someone else. Anchor: Did you ever worry, first time, that you would not want to give up those babies?Gina: It was never something that entered my mind.Anchor: Never at all?Gina: No. You go into it with the thought that this is for someone else. It is not your baby to give up. It‟s their baby from the start. And the end is the reward: The end is being able to deliver this baby and turn it over to the parents. And see, they‟ve been waiting for years for this to happen. And it finally happens when they‟re holding their own child. And it‟s so worth it.Paying a surrogate remains illegal in several parts in the United States.It‟s also against the law in most of Europe, which is why Sylvia and Michaela came all the way from Italy to the La Jolla IVF Clinic in California.Sylvia lost her uterus –and almost her life –after a miscarriage. The couple watched as embryos created through his sperm and her eggs were placed inside the body of a 30-year-old surrogate –a woman they‟d earlier communicated with from afar but never before met.The process took just minutes.Michaela: It is inconceivable to have done this maybe 30 years ago.A few weeks later, they will learn the procedure was a success –and it‟s twins.Sylvia: A miracle!The miracle has a high price. The fee for the entire surrogacy process ranges from $80,000 to well over $100,000.Of that, doctors get $9,000 to $15,000; agencies, $15,000 to $20,000; and the surrogates? First-timers get $18,000 to $25,000; experienced surrogates, up to $40,000. And in this tough economy, applications from potential surrogates are escalating. Still, Brisman says, of the 100 to 200 applications received every week, she only accepts about five to ten.Anchor: Some feminists who say, you know, this is like “womb for rent”; “mother for hire”; “it‟s like prostituting yourselves.” What‟s your reaction to that?Jennifer: It‟s, it‟s kind of offensive. It‟s insulting. It‟s very insulting.Anchor: Does it make you angry when you hear something like that?Jennifer: A little bit, yeah.Gina:It‟s a service that you‟re providing, if you want to think of it that way. More than, it‟s an exploitation of your body. You‟re not selling your body.All the same, surrogacy remains an act raising questions about our whole notion of motherhood, that unmistakable bond between mother and child.Brisman: The definition of motherhood is changing over time. Like, it‟s not necessarily the woman who gives birth is the mother. It‟s very hard for people to accept. I th ink in a few years or, you know, maybe ten years, this is just going to be old news.Lesson 2AudioScriptThe scientists who launched the Human Genome Project believed in the power of genetic information to transform health care to allow earlier diagnosis of diseases than ever before and to fuel the creation of powerful new medicines.But it was also clear that genetic information could potentially be used in ways that are。

2024年自考-自考专业(英语)-英语词汇学考试历年真题常考点试题4带答案

2024年自考-自考专业(英语)-英语词汇学考试历年真题常考点试题带答案（图片大小可任意调节）第1卷一.单选题(共20题)1.We are interested in the weather because it _______ us so directly—what we wear, what we do and even how we feel.A.benefitsB.affectsC.guidesD.effects2.“Woman” becomes “ Frau” in German, “femme” in French and “f ùnǔ” in Chinese. This example shows that in different languages the same concept can be represented by different ______ .A. soundsB.formsC.unitiesD.meanings3.Modern economics ________ the country ’s agricultural poli cies.A.undergoesB.understandsC.underliesD.undertakes4.Idioms nominal in nature have a(n) ______ as the key word in each and function as a noun in sentences.A.verbB.adjective5.Oxford Advanced Learner s Dictionary ’ , 3rd Edition (1980), is among the best-known British ______ dictionaries.A.unabridgedB.deskC.pocketD.bilingual6.______ of meaning is a process by which a word that originally had a specialized meaning has now become generalized.A.DegradationB.ElevationC.ExtensionD.Specilization7.Each of us should _______ aside a few minutes to have a rest every day.A.pushB.provideC.turnD.set8.You should help them ________ when your friends quarrel with each other.e into sighte to termse into playe to power9.Collins COBUILD English Language Dictionary (1987) has some unique features such as definition, extra column and ______.A. pronunciationB.grammar codesage examplesnguage codes10.Modern English vocabulary develops through the following channels EXCEPT ______.A.creationB.borrowingC.semantic changeD. lexical change11.The Indo-European language family is made up of the languages of the following EXCEPTA.EuropeB.the Far EastC.IndiaD.the Near East12.If you try to learn too many things at a time, you may get ________.A. concentratedB.confusedC.confirmedD.convinced13.What he told us was more of a(n) ________ than a reality.A.illusionB.demonstrationC.illustrationD.reputation14.Aliens are borrowed words which have retained their original pronunciation and spelling. Which of the following words comes from Chinese?A.BazaarB.KowtowC.RajahD.Blitzkrieg15.To write up his novel, John is looking for an environment free ________ outside distraction.A. onB.withC.fromD.in16.It took a few seconds for her eyes to ________ to the darkness.A.allocateB.adoptC.applyD.adjust17.Which of the following is NOT one of the extra-linguistic factors that cause changes in meaning?A.Cultural reason.B.Historical reason18.The differences between synonyms exist in the following areas EXCEPT ______.A.denotationB.connotationC.referenceD.application19.Generally, a dictionary covers the following contents EXCEPT ______.A. spellingB.pronunciationC.definitionD.syntactical rules20.In grammatical context, the meaning of a word may be influenced by the ______in which it occurs.A.structureB.sentenceC.phraseD.clause第2卷一.单选题(共20题)1.Among the following words, “ ______ ” contains a negative prefix.A.amoralB.de-composeC.antiwarD.foretell2.Which of the following words does NOT have suffixes?A.NorthwardB.WidenC.HappyD.Worker.3.One can figure out the meaning of “ airmail ” to be “ mail by air ” by its ______.B.morphological motivationC.semantic motivationD.etymological motivation4.Which of the following is partially converted?A. A whiteB.A drunkC.The poorD.Finals5.Washing the food down with water as a substitute ________ chewing is not a good habitA.ofB.forC.toD.from6.Which of the following statements is TRUE?A.Grammatical meaning refers to the part of speech, tenses of verbs and stylistic features ofwords.B.Unlike conceptual meaning, associative meaning is unstable and indeterminate.C.Affective meaning indicates the listener ’ s attitude towards the person or thing in questionD.Collocation cannot affect the meaning of words.7.Police are ________ the disappearance of two children.A. looking upB.looking throughC.looking intoD.looking on8.We were told that the stone figure _______ back to the 16th century was of great value.A. datedB.datingingD.kept9.Which of the following is NOT one of the context clues?A.DefinitionB.PolysemyC.SynonymyD.Antonymy.A. whatB.thatC.whichD.why11.Happiness doesn ’t alway s _______ money.A.go throughB.go in forC.go withD.go over12.There is an ambiguity in the sentence “ He is a hard businessman ” due to ______.A.polysemyB.homonymyC.synonymyD.antonymy13.A mong the following words, “ ______ ” does NOT have inflectional affixes.A. likedB.children’sC.happierD.it’s14.We cannot leave this tough job to a person ________.A.who nobody has confidenceB.in whom nobody has confidenceC.for whom nobody has confidenceD.who everyone has confidence of15.It has been years ________ I returned home.A.afterB.thatC.sinceD.when16.Which of the following is NOT one of the characteristics of idioms?A.The part of speech of each element in an idiom is very important.B.The constituents of idioms can eplaced. ’ t be rC.The word order in an idiom can ’ t be changed.D.An idiom functions as one word.breaks he wanted.A.longB.shortC.muchD.little18.The professor worked for 7 hours at a ________.A.stretchB.extendC.expandD.prolong19.Which of the following is NOT one of the main sources of new words in the present-day English vocabulary?A.The rapid development of modern science and technology.B.Social, economic and political changesC.The invasion of foreign countries.D.The influence of other cultures and languages.20.How many monomorphemic words are there in the following words? cats boss work improper triedA.1B.2C.3D.4第1卷参考答案一.单选题1.参考答案： B本题解析：affect 多作为动词来用，表示影响。

动物的英语作文

Animals are an integral part of our ecosystem,playing various roles that contribute to the balance of nature.In this essay,we will explore the characteristics and importance of animals,as well as the relationship between humans and animals.Characteristics of Animals1.Diversity:The animal kingdom is incredibly diverse,with millions of species ranging from the smallest insects to the largest mammals.Each species has its own unique set of characteristics that allow it to survive in its specific environment.2.Adaptability:Animals have evolved over millions of years to adapt to their environments.This adaptability is evident in the various forms,behaviors,and survival strategies that animals exhibit.munication:Animals communicate in a variety of ways,including through vocalizations,body language,and chemical signals.This communication is crucial for social animals to maintain group cohesion and for mating purposes.4.Reproduction:Animals reproduce to ensure the continuation of their species. Reproduction methods vary widely,from laying eggs to giving birth to live young.Importance of Animals1.Ecological Balance:Animals play a vital role in maintaining the ecological balance. They are involved in food chains and webs,where they act as predators,prey,or decomposers.2.Pollination and Seed Dispersal:Many animals,such as bees and birds,are essential for pollination and seed dispersal,which are crucial for plant reproduction and the growth of new plant communities.3.Medical and Scientific Research:Animals have been used in medical and scientific research for centuries.They provide valuable insights into human biology and diseases, leading to the development of new treatments and therapies.4.Cultural Significance:Animals have cultural significance in many societies.They are often featured in myths,legends,and religious beliefs,and are used as symbols of various human qualities.Relationship Between Humans and Animals1.Pets:Humans have domesticated certain animals,such as dogs and cats,to serve as companions.Pets provide emotional support and companionship to their owners.2.Food and Clothing:Animals are a source of food and materials for clothing.The meat industry and the use of animal products like leather and wool are significant parts of the global economy.3.Conservation Efforts:As humans have encroached on natural habitats,many animal species have become endangered.Conservation efforts are necessary to protect these species and their habitats.4.Ethical Considerations:The treatment of animals by humans has raised ethical questions about the rights of animals and the responsibilities of humans towards them.In conclusion,animals are a fascinating and essential part of our world.Understanding their characteristics,importance,and the complex relationship between humans and animals is crucial for the preservation of our planets biodiversity and the wellbeing of all living creatures.。

小学下册第14次英语第5单元期中试卷

小学下册英语第5单元期中试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.What do you call a tall building where people live?A. HouseB. ApartmentC. SchoolD. Store2.Certain plants are ______ (抗逆性强) and thrive in harsh conditions.3.What is the term for the study of plants and animals in their environment?A. EcologyB. BiologyC. ZoologyD. Botany答案:A4.The _____ (果树) has ripe fruit.5.What is the capital of the Maldives?A. MaléB. Addu CityC. FuvahmulahD. Kulhudhuffushi答案:A Malé6.His favorite hobby is ________.7.What is the name of the famous lake in Africa?A. Lake SuperiorB. Lake VictoriaC. Lake BaikalD. Lake Powell8.What is the longest river in the world?A. NileB. AmazonC. MississippiD. Yangtze9. A ________ is a large open space in a forest.10.The _______ of a flower can be very bright.11.What is the process of removing salt from seawater called?A. DistillationB. FiltrationC. DesalinationD. Evaporation答案:C12.The __________ is a famous coastal region.13.I like to read books about _______ (我喜欢读关于_______的书).14.Elements in the same column of the periodic table have similar _______.15.habitat preservation) maintains biodiversity. The ____16.The parrot can _______ (说话) like a human.17.What do we call a place where animals are kept and displayed?A. ZooB. AquariumC. ParkD. Farm答案:A Zoo18.I have a toy _______ that can spin and twirl, making me giggle.19.How many days are there in a week?A. 5B. 6C. 7D. 820.The __________ are beautiful in the spring garden. (花儿)21.The _____ (果实) on the tree is ripe.22. A polymer is a large molecule made up of many ______ units.23.Which planet is known as the Red Planet?A. EarthB. MarsC. JupiterD. Venus24.What is the process of water changing into vapor called?A. CondensationB. EvaporationC. PrecipitationD. Infiltration答案:B25.We went to the ___ (beach).26.The ________ is very cute and cuddly.27.The chemical formula for sodium dichromate is _____.28.The _____ (tulip) is blooming.29.My favorite place to relax is ______.30.I enjoy studying different cultures and their ________ (传统).31.My dad loves to watch __________. (运动)32.What is the color of a stop sign?A. BlueB. YellowC. RedD. Green33. A ______ helps to protect against predators.34. A curious ___ (小狐狸) peeks out from behind a bush.35.We have a _____ (计划) for our project.36.I want to _______ (学习) how to create a website.37.The __________ is a famous park in New York City. (中央公园)38.I want to ________ (save) money for a bike.39.The ________ can glide on the water.40.Many plants have adapted to survive in ______ climates. (许多植物已适应在极端气候中生存。

小学上册第七次英语第二单元期末试卷(含答案)

小学上册英语第二单元期末试卷(含答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.I have a ______ (娃娃) that I take everywhere. It has a pretty ______ (连衣裙) and shiny hair.2.My favorite _____ is a playful puppy.3. A ____ has a beautiful song and cheerful chirping.4.My _____ (姑姑) gave me a beautiful plant for my birthday. 我的姑姑在我生日时送了我一盆美丽的植物。

5.What do we call a person who helps sick people?A. TeacherB. ChefC. DoctorD. Artist答案:C6.The chemical formula for water is _____.7.The Earth's atmosphere is vital for ______ life.8. A ____(green belt) is a protected area around urban spaces.9.The main use of potassium nitrate is as a _____.10. A __________ is a large animal that lives in the sea and has tusks.11.She has a _____ (big) house.12.The __________ (历史的回忆) enriches our understanding.13.The _______ (猪) is often found on farms.14.What is the main language spoken in the UK?A. SpanishB. FrenchC. EnglishD. German答案: C15.The parrot has a bright ______ (羽毛).16. A ______ is a type of animal that can climb very well.17.I like to read stories about ________.18.What do you call the act of helping someone?A. AssistingB. IgnoringC. AbandoningD. Neglecting答案: A19.The sun is shining ___ (bright/dim).20.My dad is my strong _______ who teaches me right from wrong.21.I like to listen to ______ while I work.22.She is studying to be a ________.23.What do we call a story that is not real?A. Non-fictionB. BiographyC. FictionD. History答案:C24.My teacher is very ________ and helpful.25.What shape is a basketball?A. SquareB. TriangleC. CircleD. Oval答案:C26.The park is ________ and fun.27.The country known for pizza is ________ (以披萨闻名的国家是________).28.I love my _____ (玩具飞机).29.What is the term for a young animal?A. OffspringB. CubC. HatchlingD. Neonate答案:a30.The ancient Chinese invented ________ for warfare.31.What is the term for a baby horse?A. CalfB. FoalC. KidD. Lamb答案:B.Foal32.Many _______ require specific light conditions.33.The __________ (历史的视角) enriches understanding.34.My mom loves to grow _____ in her garden.35.What do you call the time when the sun goes down?A. SunriseB. DaytimeC. SunsetD. Midnight答案: C36.The chemical reaction between an acid and a base produces __________.37.ry _____ (乐观) and always looks on the bright side. She is v38.I have a small ______ (花园) where I grow ______ (蔬菜).39. A butterfly goes through four stages: egg, larva, pupa, and __________.40.I can make my toy _________ (车) go super fast down the ramp.41.The musician plays the _____ (吉他) at concerts.42.The ancient Greeks established the idea of ________ democracy.43.The _____ (greenery) is lush and vibrant.44.I like to _______ (参加) art exhibitions.45.Many plants can be grown in ______ (盆栽).46.The chemical formula for iron(III) oxide is ______.47.The flowers smell very _____. (sweet)48.The turtle swims slowly in the _______ (水).49.I have a _______ bicycle.50.What do we call a person who studies languages?A. LinguistB. PhilologistC. TranslatorD. Polyglot答案: A51.We play ___ (basketball) after school.52. A satellite orbits around a ______.53.What is the name of the famous hilltop fortress in India?A. Taj MahalB. Red FortC. Amer FortD. Qutub Minar答案:C54.The plants need sunlight and _______ (植物需要阳光和_______).55. A fish uses its ______ (鳍) to steer.56.What do we call the process of a caterpillar becoming a butterfly?A. MetamorphosisB. TransformationC. EvolutionD. Development 答案: A57.I like to play ______ (纸牌游戏) with my family during holidays.58.Which fruit is red and often mistaken for a vegetable?A. BananaB. TomatoC. CarrotD. Grape答案:b59.I like to play outside with my _______ (我喜欢和我的_______在外面玩).60.What is the capital of Kenya?A. NairobiB. KampalaC. Addis AbabaD. Dar es Salaam答案:A. Nairobi61. A __________ is a reaction that occurs without adding heat.62.The discovery of ________ changed the course of history.63.The first known civilization was in __________ (美索不达米亚).64.The capital of Greece is __________.65.The game is very ___ (exciting).66.How many days are there in a week?A. FiveB. SixC. SevenD. Eight答案: C67.I have a ________ that dances.68.My grandma bakes ____ (bread) every week.69.The ________ was a significant battle during the American Civil War.70.The ancient Romans utilized ________ (混凝土) in their construction.71.The _____ (sun/cloud) is shining.72.My dad is a _______ (职业). 他每天都 _______ (动词).73.The invention of ________ altered the landscape of communication.74.I like to organize my _________ (玩具) by color and size.75.Mount Kilimanjaro is in ________ (乞力马扎罗山位于________).76.Is he your _____ (好朋友)?77.The ________ is strong and sturdy.78. A reaction that occurs spontaneously is labeled as a ______ reaction.79. A _____ (植物凝聚力) fosters community around shared interests.80. A squirrel is often seen gathering ______ (坚果) in the fall.81.My dog loves to chase ________.82.What is the name of the bird that can mimic sounds?A. SparrowB. ParrotC. PigeonD. Eagle答案: B83.What is the name of the season when leaves fall?A. SpringB. SummerC. FallD. Winter答案: C84.Acids turn blue litmus paper ______.85.What is the name of the sweet food made from sugar and eggs?A. MeringueB. CandyC. CakeD. Pie答案: A86.The koala eats _________. (桉树叶)87.The ______ is a talented singer.88.What is 12 4?A. 6B. 7C. 8D. 9答案:c89.What do you call a triangle with all sides equal?A. IsoscelesB. ScaleneC. EquilateralD. Right答案:C90.The ancient Romans had a system of ________ known as the Republic.91.The __________ is cozy and warm. (室内)92.I help my mom with __________. (家务)93.What is the process of plants making food called?A. RespirationB. PhotosynthesisC. DigestionD. Absorption答案: B94.The deer runs fast in the _______ (鹿在_______中跑得很快).95. Depression began in __________ (1929) and affected many countries. The Grea96.My brother loves to __________ (参加) local sports events.97.The chemical formula for magnesium nitride is _______.98. A bee is busy collecting ______ (花蜜).99._____ (植物特色) attract people to gardens.100.My ________ (玩具名称) is always ready for adventure.。

英语二20年第三篇

英语二20年第三篇The 2020 English II exam's third passage discusses the issue of environmental pollution and its impact on human health. This is a critical issue that affects people all over the world, and it is important to address it from multiple perspectives.From a scientific perspective, environmental pollutionis a major concern because it can lead to a wide range of health problems. Air pollution, for example, can cause respiratory issues and exacerbate conditions such as asthma. Water pollution can lead to the spread of waterborne diseases and contamination of food sources. Additionally, soil pollution can have long-term effects on agricultural productivity and food safety. It is crucial for scientists and researchers to continue studying the impact ofpollution on human health and to develop strategies for mitigating its effects.From a public health perspective, environmentalpollution is a pressing issue that requires immediate attention. It disproportionately affects vulnerable populations, such as children, the elderly, and low-income communities. These groups often have limited access to healthcare and are more susceptible to the adverse effects of pollution. Public health officials must work to raise awareness about the dangers of pollution and advocate for policies that promote clean air, water, and soil. This includes implementing regulations on industrial emissions, improving waste management practices, and investing in sustainable energy sources.From an economic perspective, environmental pollution can have significant financial implications. The healthcare costs associated with pollution-related illnesses can place a heavy burden on individuals and healthcare systems. Additionally, pollution can negatively impact tourism, agriculture, and other industries that rely on clean and healthy environments. By addressing pollution, governments and businesses can potentially save money in the long run and create new opportunities for economic growth through sustainable practices.From a social justice perspective, environmental pollution is an issue of equity and fairness. Low-incomeand marginalized communities are often disproportionately affected by pollution due to the location of industrial facilities and waste disposal sites. This can perpetuate environmental racism and exacerbate existing social inequalities. It is essential to prioritize the needs of these communities and ensure that they have a voice in decision-making processes that affect their environment and health.From an ethical perspective, addressing environmental pollution is a moral imperative. We have a responsibilityto protect the planet and its inhabitants from harm, and allowing pollution to continue unabated is a violation of that responsibility. It is essential to consider the long-term consequences of our actions and make decisions that prioritize the well-being of current and future generations.In conclusion, environmental pollution is amultifaceted issue that requires a comprehensive andinterdisciplinary approach. By considering the scientific, public health, economic, social justice, and ethical implications of pollution, we can work towards creating a healthier and more sustainable world for all. It is essential for individuals, communities, governments, and businesses to come together to address this critical issue and prioritize the health and well-being of both people and the planet.。

小学下册D卷英语第五单元测验试卷(有答案)

小学下册英语第五单元测验试卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.I love to collect ______ (邮票) from different countries. They are very ______ (特别).2.The chemical formula for potassium hydroxide is ______.3. A flower opens in the ______.4. A _______ is a chemical reaction that involves the transfer of electrons.5.The ________ (根系) holds the plant in place.6.I love to eat ___. (salad)7.Some plants can grow in very ______ soils.8.The main gas produced during respiration is __________.9.I have a new _____ (玩具).10.She is a good ________.11.I enjoy going ________ (滑雪) in the winter.12.The ____ is often seen waddling by the water's edge.13. A reaction that occurs in an aqueous solution is called a ______ reaction.14.__________ (植物) use water and sunlight for photosynthesis.15.Chemists study the properties of _____ and their interactions.16.The cake is for my ___. (birthday)17.My favorite song to sing is ______.18.The chemical formula for potassium carbonate is ______.19.ta Stone helped decode ________ (埃及象形文字). The Rose20.The ______ (根部) serves as an anchor for stability.21.The Cold War was a period of tension between _______ and the West.22.The __________ is a famous city known for its ancient history. (开罗)23.My aunt loves to do ____ (photography).24.The ________ was a famous battle during the American Civil War.25.Read and choose the number.(读单词，选出与之意思相符的图片序号)26. A flamingo stands on one ________________ (腿).27.What do you call an animal that primarily eats meat?A. HerbivoreB. CarnivoreC. OmnivoreD. Insectivore答案:B28.Which ocean is located between Africa and Australia?A. AtlanticB. IndianC. ArcticD. Pacific答案:B29. Wall was built to protect against ________ (长城是为了保护免受________). The Grea30.I enjoy watching ________ in the garden.31.I like to _____ (dance/sing) in the shower.32.What is the study of living organisms called?A. ChemistryB. BiologyC. PhysicsD. Geography答案: B33.The _______ (蜥蜴) basks on a rock.34.The train arrives at __________ o'clock.35. A ____ has bright colors and is often seen in the forest.36.The sky is very ______ (蓝色) today.37.Which of these animals can fly?A. DogB. BirdC. FishD. Elephant答案:B Bird38.The process of photosynthesis takes place in ______.39.The _____ (蟋蟀) chirps at night in the garden.40.What is the opposite of "big"?A. HugeB. SmallC. TallD. Long答案:B41.I brush my ___ (teeth) every day.42.The flowers are ________ in the garden.43.The flowers smell _____ (good/bad).44.What is the main language spoken in Spain?A. EnglishB. SpanishC. FrenchD. German答案:B45.The cheetah can run very ______.46.What is the capital of Guinea?A. ConakryB. KankanC. NzérékoréD. Kindia答案:a47.What is the term for a person who studies the weather?A. MeteorologistB. GeologistC. BiologistD. Astronomer答案: A48.The clam burrows in the ____.49.读一读，找出不同类的单词。

小学上册第8次英语第四单元全练全测

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3.Fermentation is a process used to make ______.4.The rock cycle illustrates how rocks can change from one form to another over______.5.My grandma loves to __________ (照顾) her garden.6.What do we call the process of water changing from liquid to gas?A. EvaporationB. CondensationC. FreezingD. MeltingA7.I love going to the park with my __________. (家人)8.What do we call the act of gathering information?A. ResearchingB. InvestigatingC. LearningD. Studying9.What do you call a person who helps sick people?A. DoctorB. TeacherC. NurseD. ScientistA10.The fruit is ___. (fresh)11.mation began with Martin Luther’s _____. The Refo12.What do we call the part of the brain that controls thinking?A. CerebellumB. CerebrumC. BrainstemD. CortexB13.An endothermic process absorbs ______.14.Atoms are made up of protons, neutrons, and _____ (electrons).15.The _______ (猴子) swings on vines.16.Which animal is known for its ability to fly south for the winter?A. BearB. FishC. BirdD. Squirrel17. A __________ is a mixture of two or more gases.18.The ______ (树冠) provides shelter for birds.19.The dog wags its _____ (tail/ears) when happy.20.The __________ (历史的传承) fosters resilience.21. A buoyant object will float on ______.22.I saw a ________ dancing in the sunlight.23.I have a ___ (favorite) song.24.Which planet is known as the Blue Planet?A. MarsB. EarthC. NeptuneD. UranusB25.My ________ (玩具名称) is perfect for imaginative play.26.What do we call a small, spinning toy?A. Yo-yoB. TopC. KiteD. Frisbee27.We should _____ (recycle) plant waste.28.What do we call a baby elephant?A. CalfB. CubC. FoalD. KitA29.The _______ of a pendulum can be affected by wind.30. A chemical reaction that occurs in living organisms is called ______ chemistry.31.We are going to ___ a show. (see)32.I like to _______ (参加) community service.33.What do you call a small, furry animal that is often kept as a pet?A. HamsterB. LizardC. SnakeD. FrogA34.My mother, ______ (我的母亲), cooks delicious meals for our family.35.The ______ (霜冻) can damage tender plants.36.What do we call the process of a caterpillar becoming a butterfly?A. EvolutionB. MetamorphosisC. TransformationD. GrowthB37.The ________ has a beautiful tune that sings.38.The __________ is where seeds develop in a flower.39.The process of mixing a solute into a solvent is called ______.40.He is a scientist, ______ (他是一名科学家), who studies the stars.41.The ______ helps with the production of hormones.42.The _______ (马) can gallop quickly.43.The process of changing a liquid to a gas is called __________.44.I find ________ (古典文学) very inspiring.45.Many _______ have specific care requirements.46.My favorite animal is a ______ (马).47.Gardeners use _______ to help plants grow.48.The ________ (农业与环境保护) are interrelated.49.The Earth rotates on its ______ once every hours.50.Carbon dioxide is produced when we breathe out and during _____.51.I enjoy _____ (画画) landscapes.52.Who is known as the "Father of Medicine"?A. HippocratesB. AristotleC. GalenD. AvicennaA53.Animals that eat both plants and meat are called ______.54.The ________ was a major milestone in scientific discovery.55.What do we call a group of stars?A. GalaxyB. UniverseC. ConstellationD. NebulaC56.How do you say "谢谢" in English?A. PleaseB. HelloC. Thank youD. Goodbye57.I want to ________ my friends.58. A __________ (溶解) occurs when a substance mixes evenly in a solvent.59.The chemical symbol for chlorine is _______.60.The teacher, ______ (老师), makes learning fun and exciting.61.The __________ (历史的情感联系) enhance community.62.I love to watch _____ (蝴蝶) flutter around the flowers.63.My cousin is very __________ (幽默的) and funny.64.My sister is very __________ (敏感).65.I like to ________ (participate) in activities.66.What do we call a baby cow?A. CalfB. FoalC. LambD. Kid67. A _______ is a special type of mixture with tiny particles that never settle.68.What is the largest type of tree?A. PineB. OakC. RedwoodD. BirchC Redwood69.She is a _____ (科学家) researching climate change impacts.70.She is wearing a beautiful ___. (ring)71. A lever can increase the ______ applied to an object.72.Every Christmas, I hope for a new ____. (玩具名称)73.I enjoy _______ (阅读) books.74.Which of these is a holiday in December?A. ThanksgivingB. ChristmasC. Independence DayD. Labor DayB75.How many zeros are in one thousand?A. 1B. 2C. 3D. 476.What do we call a group of wolves?A. PackB. FlockC. HerdD. SwarmA77. A _______ is a process that occurs in cells.78.The _______ can be very fragrant.79.What do we call the act of making a choice?A. DecisionB. OpinionC. ProposalD. Suggestion80.The process of filtering separates solids from ______.81.ts use ______ to capture sunlight and produce food. (某些植物利用叶片捕获阳光并生产食物。

小学上册I卷英语第5单元真题[含答案]

小学上册英语第5单元真题[含答案]英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.I enjoy playing with my toy ________ (玩具名称) in the pool.2.What do we call the study of plants?A. BiologyB. BotanyC. ZoologyD. Ecology答案:B3.__________ (分子式) represents the ratio of elements in a compound.4.What is the opposite of "hot"?A. WarmB. ColdC. CoolD. Spicy答案:B5.The boy has a new ________.6.The _____ (美洲豹) is known for its striking spots and agility. 美洲豹以其醒目的斑点和灵活性而闻名。

7.What do we call the act of providing opportunities for success?A. EmpowermentB. SupportC. PromotionD. All of the Above答案:D8.My mom is a fantastic __________ (谈话者).9.What do we call the process of growing crops?A. AgricultureB. HorticultureC. BotanyD. Forestry10.The chemical symbol for thallium is __________.11.The process of making biofuel involves converting organic waste into _______.12. A __________ is a layer of rock below the soil.13.What is 2 + 2?A. 3B. 4C. 5D. 6答案:B14.My ___ (小狗) enjoys going for walks.15.We are going to ___ cookies. (bake)16.The _____ (野生动植物) depend on local plants for survival.17.I enjoy the sound of __________ during a gentle rain. (滴答声)18.The _____ (garden) is beautiful.19.ration of Independence was signed in ________ (1776). The Decl20.The process of fermentation produces ______ and alcohol.21.What is the capital city of Canada?A. TorontoB. OttawaC. VancouverD. Calgary答案:B22.What is the chemical symbol for gold?A. AuB. AgC. FeD. Pb答案:A Au23.Which instrument is played by blowing air into it?A. GuitarB. DrumsC. FluteD. Piano答案:C24.________ (热带雨林) has a rich variety of plants.25.I see a _____ (rabbit) in the garden.26.What do we call the annual celebration of a person's birth?A. AnniversaryB. HolidayC. BirthdayD. Festival答案:C27.I love visiting the aquarium to learn about ________ (海洋生物) and their habitats.28.The ancient Egyptians believed in the afterlife and were buried with ________ (财宝).29.What is the capital of Portugal?A. LisbonB. MadridC. BarcelonaD. Rome答案:A30.The chemical symbol for carbon is ______.31.I heard a _____ (noise/sound) outside.32. A cheetah is the fastest _______ on land, capable of incredible speed.33.The __________ (历史的传递) relies on storytelling.34.小果子) grows on trees. The ___35.I enjoy _______ (hiking) in the woods.36.The flowers in the garden attract _______ and happy bees buzzing around.bustion is a chemical reaction that produces _____.38.What is the currency used in Japan?A. YenB. RupeeC. PesoD. Dollar39.The squirrel's sharp claws help it climb trees with ________________ (轻松).40.How many zeros are in one hundred?A. OneB. TwoC. ThreeD. Four41.I find ________ (社会学) very interesting.42.What do you call the ocean that is to the east of Africa?A. Atlantic OceanB. Indian OceanC. Arctic OceanD. Pacific Ocean答案:B Indian Ocean43.The ______ is a thin layer of gases around Earth.44. A chemical reaction can be fast or ______.45.The main gas used in welding is ______.46.What is the name of the bird that cannot fly and is native to New Zealand?A. KiwiB. EmuC. OstrichD. Penguin47.What is the name of the famous scientist who proposed the theory of evolution?A. Isaac NewtonB. Albert EinsteinC. Charles DarwinD. Louis Pasteur答案:C48.My brother is interested in _______ (名词). 他想要 _______ (动词).49.The War of was fought between the USA and ________.50.biomimicry) learns from nature for innovation. The ____51. A reaction that absorbs heat is called an ______ reaction.52.The engineer, ______ (工程师), builds bridges and roads.53.What do you call a person who travels in space?A. AstronautB. PilotC. ScientistD. Explorer答案:A54.What do we call the fluffy white substance that falls from the sky in winter?A. RainB. HailC. SnowD. Sleet答案:C55.What is the opposite of big?A. LargeB. SmallC. HugeD. Tall56.The __________ (历史的探讨) encourages open dialogue.57.The chemical symbol for argon is _______.58.The __________ (历史研究) reveals important lessons.59. A _____ (猴子) can use tools to get food.60.What is the name of the famous artist known for his "Water Lilies"?A. Claude MonetB. Vincent van GoghC. Pablo PicassoD. Henri Matisse答案:A61.Which vegetable is orange and long?A. CucumberB. CarrotC. PotatoD. Eggplant62.The cake is _____ for the party. (ready)63.The cake is very ___. (rich)64.The _____ (sage) plant is drought-resistant.65.Rabbits like to dig _________. (洞)66.How many points is a touchdown worth in American football?A. 5B. 6C. 7D. 867.My brother loves going to ____ (amusement parks).68.The man is very ________.69. (88) is a famous mountain in Japan. The ____70.What is the name of the famous scientist known for his laws of motion?A. Isaac NewtonB. Albert EinsteinC. Nikola TeslaD. Stephen Hawking71.What is the largest mammal in the world?A. ElephantB. Blue WhaleC. GiraffeD. Hippopotamus答案:B72.What is the capital of South Africa?A. Cape TownB. PretoriaC. JohannesburgD. Durban答案:B73. A __________ is a landform created by the accumulation of glaciers.74.soil) is crucial for agriculture. The ____75. A __________ (温室) is a good place for plants.76.The ____ is a playful animal that loves to splash in water.77.What do we call a small, round snack made from corn?A. ChipB. PretzelC. PopcornD. Crackers78.Which of these is a popular fruit?A. TomatoB. CarrotC. AppleD. Lettuce答案:C79. A solution with a low concentration is known as a ______ solution.80.My sister loves to take care of her ______ (小猫).81.I have a _____ (遥控飞机) that can fly high.82.Cleopatra was the last pharaoh of _____.83.My ________ (玩具名称) helps me practice my spelling.84.What is the main gas we breathe?A. OxygenB. Carbon DioxideC. NitrogenD. Hydrogen答案:A85.What is the primary ingredient in a shepherd's pie?A. BeefB. ChickenC. LambD. Pork86.Light from the sun takes about eight ______ to reach us.87.The chemical formula for sodium bicarbonate is __________.88.I can ______ (count) to in Spanish.89.Certain plants can be used to create natural ______ against pests. (某些植物可以用来创建自然屏障，抵御害虫。

小学上册第十二次英语第2单元寒假试卷(含答案)

小学上册英语第2单元寒假试卷(含答案)英语试题一、综合题(本题有50小题，每小题1分，共100分.每小题不选、错误，均不给分)1 Acids taste __________.2 The Stone Age is known for the use of ________ tools.3 What is the main ingredient in a salad?A. MeatB. VegetablesC. FruitD. Bread答案: B4 I like to practice ______ every day.5 The __________ (历史的连接) builds relationships.6 The _____ (虫子) play a role in pollinating plants.7 The chemical symbol for hydrogen is ______.8 The bear hibernates in a _____ cozy cave.9 What is the name of the holiday in February?A. HalloweenB. Valentine's DayC. ChristmasD. New Year答案: B10 What do we call the place where animals are kept for public viewing?a. Zoob. Aquariumc. Farmd. Jungle答案:a11 What is the name of the fairy tale character who leaves a glass slipper?A. Snow WhiteB. CinderellaC. RapunzelD. Little Red Riding Hood答案:B12 In conclusion, spring is a wonderful season full of ______ and joy. I can't wait for it to come every year!13 The chemical symbol for berkelium is _____.14 What do we call a collection of books?a. Libraryb. Storec. Officed. School答案:a15 My sister is very __________ (热情的) about her hobbies.16 My mom is ______ (cooking) dinner.17 My cousin is a wonderful __________ (讲故事的人).18 I created a new adventure for my toy ____. (玩具名称)19 What do you call a large area of sand?A. DesertB. BeachC. DuneD. Oasis答案:A20 The ______ (霜冻) can damage tender plants.21 The flowers in the garden are very _______ (花园里的花非常_______).22 The ancient Romans enjoyed _____ in their amphitheaters.23 What is the name of the famous Egyptian queen?A. NefertitiB. CleopatraC. HatshepsutD. Tutankhamun答案:B24 The __________ (历史的探寻) leads to discovery.25 What is the name of the famous scientist known for his work on radioactivity?A. Marie CurieB. Albert EinsteinC. Isaac NewtonD. Charles Darwin答案: A26 What animal is known for having stripes?A. LionC. BearD. Elephant答案:B27 How many sides does a hexagon have?A. 4B. 5C. 6D. 7答案:C28 We will go to the _____ (beach).29 The signing of the Magna Carta occurred in __________. (1215年)30 ic Ocean is the ________ (最大的) ocean. The Paci31 The bee is essential for _______ pollination.32 I hope to visit _______ (地方) someday. It’s known for its beautiful _______ (风景).33 What is the name of the small, winged creature that is often associated with magic?A. FairyB. ElfC. GoblinD. Troll答案:A34 The conductor, ______ (指挥), leads the orchestra.35 My brother has a ______ pet hamster.36 My sister is a ______. She loves to sing.37 Which vegetable is orange and long?B. CarrotC. BroccoliD. Spinach答案:B38 The invention of ________ has greatly advanced communication technology.39 I often _______ (参加) community events on weekends.40 My brother is a great __________ (运动员) in basketball.41 I love to draw and paint. My favorite thing to draw is ________ (动物), especially ________ (猫) and dogs.42 We have a family _______ (聚会) every year.43 In ancient China, the __________ was a symbol of wisdom. (龙)44 What is the main ingredient in a salad?A. FruitB. LettuceC. MeatD. Bread答案:B45 A _____ (植物联盟) can promote conservation efforts.46 The smallest unit of a compound is a _______.47 What is the name of the famous composer known for "The Nutcracker"?A. Johann StraussB. Igor StravinskyC. Pyotr Ilyich TchaikovskyD. Ludwig van Beethoven48 The __________ (历史的启示性探讨) foster understanding.49 The capital of Sweden is __________.50 The cat is _______ (在) the tree.51 The __________ (历史的遗产) is a shared treasure.52 A ______ occurs when magma from inside the Earth erupts.53 The ______ (生态系统) relies on balance.54 What is the main function of leaves?A. PhotosynthesisB. ReproductionC. GrowthD. Movement答案: A55 What is the main ingredient in pizza dough?A. RiceB. FlourC. CornD. Oats答案: B56 An animal that can live in water and on land is an ______.57 The turtle crawls slowly on the ______.58 My sister enjoys __________ (舞蹈) classes after school.59 Martin Luther King Jr. gave his famous "I Have a Dream" speech in _____ (1963).60 We play ________ (volleyball) at the beach.61 A __________ is formed through the interaction of wind and water on soil.62 The __________ is a critical area for biodiversity.63 I write letters to my ____.64 The boiling point of water is ______ degrees Celsius.65 The __________ (历史的理解深度) enriches perspectives.66 How many sides does a square have?A. ThreeB. FourC. FiveD. Six67 The symbol for nickel is _____.68 The discovery of ________ has had significant implications for health and wellness.69 A ______ is a type of rodent.70 How do you say "thank you" in Japanese?A. GraciasB. MerciC. ArigatoD. Danke71 My sister loves __________ (学术).72 The __________ is the part of the plant that releases oxygen.73 The bat uses echolocation to find ______ (食物).74 Gases do not have a fixed _____.75 This girl, ______ (这个女孩), loves to draw and paint.76 How many players are on a basketball team?a. Fiveb. Sixd. Eight答案:A77 A _______ (猴子) is known for its playful behavior.78 A chemical that can accept electrons is called an ______.79 ers close at ______ (夜晚). Some flo80 What is the capital of Mozambique?A. MaputoB. BeiraC. NampulaD. Tete答案: A81 _____ (sustainable) practices can reduce waste.82 ts can reproduce through ______ rather than seeds. (某些植物可以通过扦插而不是种子繁殖。

小学上册第九次英语第二单元综合卷[有答案]

小学上册英语第二单元综合卷[有答案]考试时间：90分钟（总分:120）B卷一、综合题(共计100题共100分)1. 填空题：The ________ is known for its speed.2. 填空题：My brother is learning to ________ (打鼓).3. 选择题：What do you call a baby cat?a. Puppyb. Kittenc. Cubd. Chick答案:b4. 填空题：My dad is a _____ (工程师) who solves complex problems.5. 填空题：The __________ (历史的洞察) opens eyes.6. 选择题：What is 6 x 3?A. 18B. 15C. 12D. 21答案:A7. 选择题：What is the capital of Micronesia?a. Palikirb. Wenoc. Yapd. Pohnpei答案:a8. 填空题：Do you like _______ (冰淇淋)?9. 听力题：The snowman is _____ in the yard. (standing)10. 听力题：An ion is an atom with a _____ charge.11. se invented ________ around 100 AD. 填空题：The Civi12. 听力题：A _______ helps illustrate the concept of buoyancy.13. ecological footprint) reflects human activity's impact. 填空题：The ____14. 填空题：My pet ______ (兔子) loves to eat fresh greens.15. 填空题：The ______ of a plant can tell you a lot about its habitat. (植物的叶型可以告诉你很多关于其栖息地的信息。

小学上册第九次英语第4单元测验卷

小学上册英语第4单元测验卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1._____ (seasonal) changes affect plant growth.2.The __________ (历史的记忆) informs our future.3.The bird is perched high in the ______.4. A chemical reaction often involves a change in ______.5.The trees in the _______ provide a cool shade on sunny days.6.The ______ of a plant can tell you about its environment. (植物的特征可以告诉你它的环境。

)7.The ______ (植物的特征) can inform garden design.8.What is the main language spoken in the USA?A. SpanishB. EnglishC. FrenchD. German9.Which book series features a boy named Harry?A. The Chronicles of NarniaB. Percy JacksonC. Harry PotterD. The Hobbit10. A _______ is a reaction that releases energy in the form of heat.11.What do we call the main character in a story?A. ProtagonistB. AntagonistC. Supporting characterD. VillainA12. A __________ is known for its ability to spin webs.13.What is the value of 3 + 3 × 3?A. 9B. 12C. 15D. 18B14.He is a musician, ______ (他是一位音乐家), and plays the guitar.15.The stars are ___ (twinkling/shining) in the night.16.The ________ plays in the wind and makes music.17.I want to visit the ________.18.What do we call a picture made by sticking various materials together?A. CollageB. MosaicC. PaintingD. Sculpture19.The owl is ______ (夜间活动的) and hunts at night.20.I want to ______ how to ride a horse. (learn)21.My mom cooks __________ for dinner. (美味的食物)22.What is the capital of Russia?A. MoscowB. St. PetersburgC. KievD. MinskA23.collaborative initiative) addresses shared concerns. The ____24.The __________ is the largest ocean on earth.25.The weather is _____ (sunny/cloudy) today.26.The _______ (The Civil Rights Movement) sought to eliminate racial inequality.27.In summer, I enjoy going to the ______ (海滩) to build ______ (沙堡) and swim in the ______ (海水).28. A bird builds its _______ high in the trees. is the ________ (亚洲是________) continent in the world.30.The __________ (文化多样性) enriches society.31.What do you call the study of the universe?A. AstronomyB. AstrologyC. PhysicsD. GeographyA32.What do we call the process of plants making their food?A. DigestionB. PhotosynthesisC. RespirationD. FermentationB33.The _____ (叶绿素) in leaves helps with photosynthesis.34.What do we call a person who composes music?A. MusicianB. ComposerC. SingerD. Performer35.The fruits are fresh and ___. (juicy)36.The chemical formula for lead(II) nitrate is __________.37.Indicators are substances that change color in the presence of an ______.38.What is the main ingredient in pesto sauce?A. BasilB. GarlicC. Olive oilD. Pine nuts39.Many plants are well-suited for container gardening, offering flexibility in ______. (许多植物适合容器园艺，提供种植的灵活性。

小学上册第13次英语第1单元测验卷(有答案)

小学上册英语第1单元测验卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The first electric vehicle was built in the _______ century. (19)2.What is the capital city of the Netherlands?A. AmsterdamB. RotterdamC. UtrechtD. The Hague答案:A3.The ______ is a famous scientist.4.The _____ (钥匙) is on the counter.5.My _______ (金鱼) is very playful.6.The squirrel collects nuts for _________. (冬季)7.My favorite color is _____ (blue/sit).8.What color do you get when you mix blue and yellow?A. GreenB. PurpleC. OrangeD. Brown9.What is the capital of Malaysia?A. Kuala LumpurB. JakartaC. BangkokD. Manila10.What is the purpose of a map?A. To eatB. To navigateC. To sleepD. To read11.The _____ (花粉) helps in the reproduction of plants.12.I enjoy _______ (骑马) on weekends.13.What do you call a group of ducks?A. FlockB. TeamC. GaggleD. Raft14.He has a ______ for his birthday. (party)15.When it snows, I love going ________ (滑雪) with my family. It’s thrilling and ________ (刺激的).16.What do you call a person who studies sociology?A. SociologistB. AnthropologistC. PoliticianD. Historian答案:A17.What do we call a person who creates comic books?A. CartoonistB. IllustratorC. AuthorD. Graphic Novelist答案:D18.The ______ is a key part of the food chain.19.The _______ (The Japanese Internment Camps) were established during WWII.20.What do you call the natural satellite of Earth?A. StarB. PlanetC. MoonD. Comet答案:C21.I like to make ______ for my family.22.ts can reproduce through ______ rather than seeds. (某些植物可以通过扦插而不是种子繁殖。

小学上册第3次英语第1单元期末试卷

小学上册英语第1单元期末试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The __________ (历史的教育意义) shapes future generations.2.The stork brings _________ (宝宝).3.My uncle shares his __________ (经验) in business.4.Objects in motion tend to stay in ______.5.The girl is very ________.6.What is the largest ocean in the world?A. Atlantic OceanB. Indian OceanC. Arctic OceanD. Pacific OceanD7.The rabbit's fur is very ______ (软).8.What do you call a story that teaches a lesson?A. FableB. NovelC. PoemD. Myth答案:A9.I like to feed my ______ in the morning.10.Gardening can also provide opportunities for environmental ______ and education. (园艺还提供了环境保护和教育的机会。

)11.My ______ loves to help others succeed.12.What do we call the process of recycling waste materials?A. CompostingB. ReusingC. ReducingD. UpcyclingA13. A __________ is a type of chemical bond where electrons are shared.14.They are _____ (making) a fort.15.My bunny eats ______ (胡萝卜) every day.16.What color is the sky on a clear day?A. GreenB. BlueC. YellowD. RedB17.What do we call the time of year when flowers bloom?A. WinterB. SpringC. SummerD. Autumn18.The ________ (地方特色食品) are worth trying.19.What do we call the study of how people interact with each other?A. SociologyB. PsychologyC. AnthropologyD. EconomicsA20.We had ______ (fun) at the museum.21.What do we call a person who studies the psychological effects of trauma?A. Trauma PsychologistB. Clinical PsychologistC. PsychiatristD. Social WorkerA22.The _____ (青蛙) catches flies with its tongue.23. A ______ is a geological feature that rises abruptly.24.What do we call a house for fish?A. TankB. PondC. AquariumD. SeaC25.The Earth's atmosphere protects us from ______.26.I want to visit ________ (博物馆).27.The chemical symbol for lithium is ______.28. A ____(public-private partnership) leverages resources for community benefit.29. A __________ is a reaction that requires heat to occur.30.The flowers in the vase are very _______ (花瓶里的花非常_______).31.What is the largest continent?A. AfricaB. AsiaC. EuropeD. South AmericaB32.The rabbit hops around the _________. (花园)33.What is the capital of Cuba?A. HavanaB. SantiagoC. CamagüeyD. Holguín34.ts produce ______ that can be used in cooking or for flavoring dishes. (某些植物可以产生用于烹饪或调味的香料。

小学上册第12次英语第六单元真题

小学上册英语第六单元真题英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.Martin Luther King Jr. fought for _____ rights.2.The sun sets in the ________.3.What is the opposite of "fast"?A. QuickB. SlowC. RapidD. Speedy4.What is 4 × 3?A. 10B. 12C. 14D. 165.The ______ helps with the sense of taste.6.The three states of matter are solid, liquid, and _______. (气体)7.What do you call the person who writes books?A. PainterB. AuthorC. MusicianD. DirectorB8.I enjoy playing with my ________ blocks.9.The Himalayas are still rising because the tectonic plates are ______.10.The ________ is very friendly.11.The _____ (狮子) has a powerful roar.12. A reaction that occurs at low temperatures is called a ______ reaction.13.I can ______ a song on the guitar. (play)14.The cake is _____ (delicious/yummy).15.The _____ (兔子) is known for its long ears.16.What is the term for a group of lions?A. PackB. PrideC. FlockD. HerdB17.What is a young dog called?A. KittenB. PuppyC. CubD. Foal18.The _____ (小狗) is barking at the mailman.19.The owl can turn its head almost _______ (完全) around.20.What is the name of the ancient civilization that built pyramids in Egypt?A. MayansB. AztecsC. EgyptiansD. GreeksC Egyptians21.The _____ (海洋) is vast.22.My sister is a ______. She loves to host parties.23.What do you call a group of lions?A. PackB. PodC. PrideD. FlockC24.My favorite type of music is ______.25.What do we call a person who studies space?A. AstronomerB. GeologistC. MeteorologistD. Biologist26.She is _____ (studying) for exams.27.The __________ (历史的开放性) invites exploration.28.The Mediterranean Sea is between Europe and _______.29.The dog is _____ (barking).30.What is the largest continent?A. AfricaB. AsiaC. EuropeD. Australia31.Some _______ are used for making salads.32.The horse runs freely in the ______ (田野). It is very ______ (快乐).33.What do we call the device used to cook food using electricity?A. OvenB. StoveC. MicrowaveD. ToasterC34.Planting _____ (香味植物) can attract butterflies to the garden.35.What is the capital of Venezuela?A. CaracasB. MaracaiboC. ValenciaD. BarquisimetoA36.When I go to bed, I hug my ____. (毛绒玩具)37.What is the capital of Russia?A. KyivB. MoscowC. MinskD. TbilisiB38.What is the name of the famous mountain range in South America?A. RockiesB. AndesC. AlpsD. HimalayasB Andes39.My favorite snack is ________ (巧克力) after school.40.Rainforests are known for their rich ______.41.What is the process of turning a solid into a liquid?A. FreezingB. MeltingC. EvaporationD. CondensationB42.What type of animal is a frog?A. MammalB. ReptileC. AmphibianD. Bird43.The _____ (花蜜) attracts bees and butterflies.44.What is the capital of India?A. MumbaiB. DelhiC. KolkataD. Bangalore45.The chemical formula for hydrochloric acid is _______.46.Certain plants are capable of surviving long periods of ______ without water. (某些植物能够在缺水的条件下存活很长时间。

小学上册第七次英语第三单元期末试卷

小学上册英语第三单元期末试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.My mom loves to plant ______ in the garden.2.What is the term for a baby chicken?A. PuppyB. KittenC. ChickD. Calf3.What do we call the part of a story that introduces the characters and setting?A. ClimaxB. ConclusionC. ExpositionD. ConflictC4.What is the opposite of cheap?A. ExpensiveB. AffordableC. ReasonableD. Costly5.I like to take pictures with my ________ (玩具名称).6.The _____ (青蛙) catches flies with its long tongue. 青蛙用它的长舌头抓住苍蝇。

7.The weather is _______ for a picnic.8. A ______ is a scientific statement that summarizes a pattern.9. A chemical reaction can be influenced by the presence of a ______.10. A monkey can _______ (爬) trees easily.11.Many fruits grow from _____ (树) or bushes.12.What is 10 - 3?A. 5B. 7C. 8D. 6B13.In chemistry, we measure volume in ______.14.The dog is ______ at the squirrel in the yard. (barking)15.My aunt is a ______. She enjoys cooking.16. A wheel makes it easier to _______ things.17.Chromatography is a method used to separate _______. (色素)18.What is the capital city of Bangladesh?A. DhakaB. ChittagongC. KhulnaD. Sylhet19.What is the capital of Madagascar?A. AntananarivoB. MahajangaC. ToamasinaD. AntsirananaA20. A dog wags its _______ (尾巴) when happy.21.The _____ (树叶) change color in the fall.22.The chemical formula for butane is ________.23.My brother is my adventurous _______ who tries new things.24.I love to watch the __________ fall from the sky in winter. (雪)25.I enjoy baking cakes with my mom for special ________ (庆祝活动).26.My dad is a strong __________ (榜样) for me.27.What is the name of the famous bakery in "The Great British Bake Off"?A. The Cake ShopB. The Bread BasketC. The TentD. The Pastry PlaceC28.The _____ (蜗牛) leaves a slimy trail behind.29.I enjoy learning about science experiments. They show us how things work in our world. One experiment I found exciting was __________ because it demonstrated__________.30.I can’t wait to show my friends my new ____. (玩具名称)31.The _____ (园艺技巧) can be learned through practice.32.In geography, a __________ is a large area with similar climate and vegetation.33.The Earth's crust floats on the __________.34.What do you call the place where fish are kept?A. PondB. AquariumC. OceanD. RiverB35.The ______ (果汁的提取) can be done in various ways.36.What is the result of 15 divided by 3?A. 3B. 4C. 5D. 637.The pelican dives into the _______ (水).38.My dad enjoys talking about ____ (history).39.The _______ (猴子) loves to eat fruits.40.What is the boiling point of water?A. 0°CB. 50°CC. 100°CD. 200°CC41.What do we call an animal that can live both on land and in water?A. ReptileB. MammalC. AmphibianD. Fish42.My brother is passionate about ____ (computers).43.What is the capital city of Brunei?A. Bandar Seri BegawanB. Kuala BelaitC. SeriaD. Tutong44.The monkey is ________ in the tree.45.We need to _____ (clean/cook) the house.46.What is the term for a scientific test to prove or disprove a hypothesis?A. ExperimentB. ObservationC. TheoryD. ConclusionA47.The _____ (章鱼) is a fascinating sea creature.48.The __________ was a conflict between the North and South in the United States.49.Which instrument has strings?A. FluteB. DrumsC. ViolinD. Trumpet50.She likes to collect ___. (stickers)51.My friend’s dad, ______ (我朋友的爸爸), is a lawyer.52.In a chemical reaction, products are formed from ______.53.The __________ (历史人物) like Nelson Mandela have inspired many.54.The ancient civilizations of ________ are known for their achievements in math.55.In conclusion, my favorite season is ______ because it brings joy and happiness. I look forward to it every year!56.What is the capital of Italy?A. VeniceB. FlorenceC. RomeD. MilanC57.What is the main ingredient in sushi?A. PastaB. RiceC. BreadD. Meat答案:B58.The atomic structure of an atom includes the nucleus and _____ (electron cloud).59. A sound wave can be heard when it travels through ______ (air).60.I want to grow a ________ in my room.61. A ____ is a small animal that makes a chirping sound.62.She is _______ (smiling) at the camera.63. A _____ is a large area of land used for agriculture.64.What is the name of the superhero who wears a cape and flies?A. BatmanB. SupermanC. Spider-ManD. Iron Man65. A ________ (泥土) test can improve growth.66.The ________ was a key event in the history of civil rights in the United States.67.What do we call the smallest unit of life?A. CellB. AtomC. MoleculeD. Organ68.I saw a ________ in the flower bed.69.Did you see that _____ (小兔) hopping in the garden?70.My ________ (玩具) is very lightweight.71.Hydrogen ions give acids their ________ properties.72.The ______ is home to many fish.73.The country known for its wildlife is ________ (以野生动物闻名的国家是________).74.How many players are on a football (soccer) team?A. TenB. ElevenC. TwelveD. Thirteen75.The kitten chases a ______.76.My favorite color is ______. (blue)77.The sun is ______ in the morning. (rising)78.What is the name of the famous singer known for "I Will Always Love You"?A. Mariah CareyB. Whitney HoustonC. Celine DionD. AdeleB79.The ______ helps break down food in the stomach.80.I have _____ of friends in my class. (lots)81.What is the largest desert in the world?A. SaharaB. GobiC. ArabianD. AntarcticD Antarctic82.__________ are used in cleaning products for stain removal.83.My _______ (金鱼) has shiny scales.84.The ________ was a significant moment in the history of labor rights.85.The _______ (The 19th Amendment) granted women the right to vote in the US.86.What is the opposite of fast?A. QuickB. SlowC. SpeedyD. RapidB87.My grandma loves to tell stories about ____.88.The sun is very ________ today.89.The _______ of an object can be calculated using its dimensions.90.The process of rusting is a common example of _______.91.My pet bird can _______ (模仿) sounds.92.I want to ________ (make) a difference.93.The puppy is ______ to the sound. (curious)94.The _____ of a star can indicate its temperature.95.What do we call the study of the earth and its features?A. GeographyB. GeologyC. EcologyD. MeteorologyA96.The parakeet loves to play with _______ (玩具).97.What do you call the fear of heights?A. ClaustrophobiaB. AcrophobiaC. AgoraphobiaD. NyctophobiaB98.What do we call the time it takes for the Earth to complete one rotation?A. YearB. DayC. MonthD. HourB99.The _______ of a wave can be described by its frequency and amplitude.100.What is the capital of Belgium?A. AmsterdamB. BrusselsC. LuxembourgD. Paris。

成都2024年07版小学五年级第4次英语第三单元真题

成都2024年07版小学五年级英语第三单元真题考试时间：90分钟（总分:140）A卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、What is the main ingredient in soup?A. WaterB. SaltC. SugarD. Oil答案: A2、What is 3 + 6?A. 8B. 9C. 10D. 11答案:A3、填空题：This girl, ______ (这个女孩), enjoys acting in plays.4、填空题：My grandma loves to __________ (照顾) her plants.5、ts are _____ (外来物种) that can be invasive. 填空题：Some pla6、听力题：The process of photosynthesis uses __________ and sunlight.7、填空题：Did you hear the _____ (小狗) barking at the mailman?8、填空题：Flowers attract _____ (butterfly) and bees.A ______ (社区花园) brings people together.10、What is the name of the current U.S. president?A. George W. BushB. Barack ObamaC. Joe BidenD. Donald Trump答案:C11、听力题：The chemical formula for ammonium nitrate is ______.12、 (Celtic) people inhabited parts of Europe thousands of years ago. 填空题：The ____13、What do you call a story that explains how something came to be?A. LegendB. MythC. FableD. Tale14、听力题：I like to ___ (write) letters.15、What is the name of the tallest building in the world?A. Empire State BuildingB. Burj KhalifaC. CN TowerD. Eiffel Tower答案:B16、听力题：The clouds look ______ (gray) before the storm.17、选择题：What is the name of the famous mountain in the United States?A. Mount RushmoreB. Mount KilimanjaroC. Mount EverestD. Mount Fuji18、填空题：The _____ (花) blooms beautifully in spring.What is the currency used in the USA?A. DollarB. EuroC. YenD. Pound20、听力题：The chemical reaction that occurs in batteries is called _____.21、What do you call the device used to take photos?A. CameraB. PhoneC. TabletD. Computer答案: A22、听力题：A frog starts its life as a ______.23、填空题：The __________ is a large body of ice moving slowly down a mountain. (冰川)24、听力题：A solution with a pH of is very ______.25、听力题：The Sahara Desert is one of the hottest _______ on Earth.26、听力题：A ____ is a nocturnal animal known for its keen eyesight.27、听力题：A _______ can measure the temperature of a gas.28、填空题：The _____ (草坪) is great for playing games.29、填空题：Plants need _____ (光照) for photosynthesis.30、What do we call a story that is not true?A. FactB. FictionC. Non-fictionD. Biography答案: B31、What do you call the study of the human mind and behavior?A. SociologyB. PsychologyC. AnthropologyD. Philosophy32、听力题：The reaction of acids with metals is often used to produce ______.33、填空题：My family has a pet _______ (动物). Its name is _______ (名字). It loves to _______ (动词) around the house.34、填空题：_____ (花期) varies for different plants.35、听力题：A __________ is crucial for the development of civilizations.36、填空题：My cat likes to chase _______ (光点).37、听力题：The chemical formula for methane is ________.38、Which month comes after January?A. FebruaryB. MarchC. AprilD. May答案:A39、How do you say "goodbye" in German?A. AdiósB. Auf WiedersehenC. Au revoirD. Arrivederci40、填空题：I like to play with my ____ in the park. (玩具类型)41、听力题：The boiling point of water is _______ degrees Celsius.42、填空题：The ________ is very friendly and loves to play.43、填空题：The _____ (兔子) loves to eat carrots and greens.44、填空题：My teacher is _______ and makes learning fun.45、听力题：The main gas produced during combustion is __________.46、填空题：A starfish can regrow lost ________________ (臂).47、What is the capital of Latvia?A. VilniusB. RigaC. TallinnD. Helsinki答案:B48、What is the name of the famous clock tower in London?A. Big BenB. The ShardC. The GherkinD. The Tower of London答案:A49、听力题：The butterfly is ___ (flapping) its wings.50、填空题：The ______ (树叶) fall off in winter for some trees.51、填空题：The invention of the steam engine was crucial for the __________ (工业革命).52、What do we celebrate on the Fourth of July in the United States?A. ThanksgivingB. Independence DayC. New YearD. Memorial Day答案: B. Independence Day53、What is 100 75?A. 15B. 25C. 35D. 45答案: B54、What do you need to write on paper?A. PaintB. PencilC. ClayD. Glue答案:B55、填空题：A _____ is a large expanse of sand.56、What do you call a baby dolphin?A. CalfB. PupC. KitD. Fawn答案:A57、What do we call a person who studies plants?A. BiologistB. BotanistC. ZoologistD. Ecologist答案: B58、填空题：The ancient Romans wrote their laws on ______ (青铜板).59、填空题：I have always dreamed of going on a ______ vacation. If I could go anywhere in the world, I would choose ______. This place is famous for its beautiful ______ and exciting activities.60、填空题：The seagull flies over the _______ (海洋).61、 (Roman) Empire had a complex system of roads. 填空题：The ____62、What do we call a young llama?A. CalfB. KidC. FoalD. Pup答案:A. Calf63、What is the capital of Italy?A. VeniceB. FlorenceC. RomeD. Milan答案:C64、填空题：I can ______ (做到) my best in everything I try.65、听力题：__________ can be found in deserts, forests, and oceans.66、填空题：The _____ (cypress) tree grows near water.67、听力题：The ________ (workshop) enhances learning.68、听力题：A _______ is a property that describes how easily a substance can be magnetized.69、What is the first letter of the English alphabet?a. Ab. Bc. Cd. D答案:A70、填空题：The __________ was so bright, I had to squint my eyes. (阳光)71、听力题：A chemical that can produce gases is called a ______.72、What do you call a baby cat?A. PuppyB. KittenC. CubD. Foal答案:B73、填空题：The first photograph was taken in _______. (1826年)74、听力题：We go to _____ (school/home) every day.75、What is the name of the famous painting of a woman with a mysterious smile?A. The Girl with a Pearl EarringB. Mona LisaC. The Birth of VenusD. The Last Supper答案：B76、What is the term for animals that sleep during the winter?A. HibernateB. MigrateC. EstivateD. Adapt答案:A77、What is the name of the longest bone in the human body?A. FemurB. TibiaC. HumerusD. Radius78、填空题：During the holidays, I visit my ______ (祖父母) in the countryside. They have a big______ (花园) where I can play.79、填空题：I can fold my ________ (玩具) into different shapes.80、填空题：My dad is a wonderful __________ (父亲) who supports my dreams.81、ts can ______ (利用) sunshine more efficiently. 填空题：Some pla82、听力题：My friend is ______ (smart) and funny.I can create my own ________ (玩具) using blocks.84、填空题：I like to race my _________ (玩具车) with my friends at the park.85、What type of animal is a dolphin?A. FishB. MammalC. ReptileD. Amphibian答案:B86、What color is the center of a target?A. RedB. BlueC. YellowD. Black答案:A87、听力题：The chemical symbol for cobalt is _______.88、What is the name of the famous American Civil Rights leader?A. Malcolm XB. Martin Luther King Jr.C. Rosa ParksD. Nelson Mandela答案: B. Martin Luther King Jr.89、What is the longest river in the world?A. AmazonB. NileC. YangtzeD. Mississippi答案:B90、填空题：My teacher says we should always be respectful and call others __.(我的老师说我们应该始终尊重他人并称呼他们为。

广州2024年09版小学3年级第4次英语第五单元期中试卷

广州2024年09版小学3年级英语第五单元期中试卷考试时间：100分钟（总分:100）B卷考试人：_________题号一二三四五总分得分一、综合题(共计100题共100分)1. 选择题：How many planets are in our solar system?A. EightB. NineC. TenD. Eleven2. 听力题：The process of turning a liquid into a gas is called _______.3. 填空题：The _____ (根部) store energy for the plant.4. 听力题：The Earth revolves around the Sun in ______ days.5. 听力题：The process by which plants make their food is called _______.6. 填空题：I saw a _____ (小猫) playing with a piece of string.7. 填空题：I love sunny ______ (天气) because I can play outside.8. 填空题：The _____ (花坛) is filled with colorful blooms.9. 选择题：What do we call a person who studies the effects of drugs on the body?A. PharmacologistB. ToxicologistC. BiochemistD. Chemist答案: A10. 听力题：I want to learn how to ______ (skate) on ice.11. 选择题：What do we call the act of sharing a story?A. NarratingB. TellingC. RelatingD. Communicating答案:A12. 填空题：Many animals depend on plants for ______ (食物).13. 选择题：What do you call the king of the jungle?A. TigerB. ElephantC. LionD. Bear14. 选择题：What is the primary function of leaves on a plant?a. To provide supportb. To absorb waterc. To make foodd. To store nutrients答案:c15. 填空题：I love to watch the _____ in the sky.16. 听力题：The first female Prime Minister of the UK was _______ Thatcher.17. 填空题：A goldfish can recognize its ______ (主人).18. 填空题：A rabbit can be very ______ (活泼) and playful.19. 听力题：I have a ___ (story) to share.20. 选择题：What do we call the energy from the sun?A. Solar energyB. Wind energyC. Nuclear energyD. Geothermal energy答案:A21. 听力题：Honey is made by ______.22. 听力题：I have a ___ (collection) of seashells.23. 选择题：What is the chemical symbol for water?A. CO2B. O2C. H2OD. NaCl答案: C24. 听力题：The chemical formula for sodium nitrite is ______.25. 听力题：The ______ is very good at solving problems.26. 填空题：My brother is a big __________ of superheroes. (粉丝)27. 听力题：My friend is a ______. He enjoys building things.28. 填空题：I call my grandfather _____ (爷爷).29. 选择题：Which animal is known for its ability to change colors?A. ChameleonB. ElephantC. TigerD. Bear30. 选择题：What do we call the line that divides the Earth into two halves?A. EquatorB. Prime MeridianC. Tropic of CancerD. Arctic Circle答案:A31. 听力题：We have a family ___. (tradition)32. 听力题：A __________ is formed from the deposition of sediments in a lake.33. 听力题：The ______ helps protect living organisms from harmful radiation.34. 选择题：What is the color of a typical fire truck?A. BlueB. YellowC. RedD. White35. 听力题：The chemical symbol for osmium is ______.36. 填空题：My sister enjoys __________ (参加) music lessons.37. 填空题：I saw a ________ in the grass today.38. 填空题：At the beach, I found a _______ (小螃蟹) hiding in the sand.39. 填空题：My brother is very __________ (乐于助人的) to others.40. 填空题：A playful ___ (小猫) pounces on a toy.41. Read and colour.(看词涂色.)42. 填空题：A _____ (狮子) is known as the king of the jungle.43. 填空题：The capital of Australia is ________ (堪培拉).44. 填空题：The first person to successfully climb Mount Everest was _______. (希拉里)45. 填空题：Dolphins are very _______ (聪明的).46. 填空题：The chihuahua is a very _______ (小型) dog breed.47. 听力题：I see a _____ (鱼) in the tank.48. ts grow best in ______ (潮湿) conditions. 填空题：Some pla49. 听力题：The game is very ________.50. 听力题：I need a _____ (chair/table) to sit on.51. 选择题：Which animal is known for its stripes?A. LeopardB. TigerC. BearD. Lion52. 选择题：What is 3 x 4?A. 10B. 11C. 12D. 13答案: C. 1253. 填空题：I like to _______ my family.54. 填空题：I have a toy _______ that can bounce high.55. 填空题：The rabbit's hearing is very ______ (灵敏).56. 听力题：The chemical formula for propylene glycol is ______.57. 听力题：A solution is a mixture where one substance ______ in another.58. 选择题：What is a baby dog called?A. KittenB. PuppyC. CalfD. Chick59. 填空题：A _______ (小马) trots along the path.60. 选择题：What do we call the first meal of the day?A. LunchB. DinnerC. BreakfastD. Snack61. 填空题：I love to watch the __________ fall from the sky in winter. (雪)62. 填空题：The goldfinch has a cheerful ________________ (歌声).63. 选择题：What is the opposite of open?A. CloseB. ShutC. BlockD. Both A and B答案:D64. 选择题：What is the capital of Sri Lanka?A. ColomboB. KandyC. GalleD. Jaffna答案:A. Colombo65. 听力题：The _______ can thrive in a variety of conditions.66. 选择题：What is 3 - 1?A. 2B. 3C. 4D. 567. 听力题：An astronaut travels into _____ to explore space.68. 听力题：A __________ is a geological structure formed by volcanic activity.69. 听力题：The chemical formula for magnesium hydroxide is _______.The __________ (气象学家) studies weather patterns.71. 听力题：She is _____ (reading) a storybook.72. 选择题：What do you call a place where you can borrow books?A. SchoolB. LibraryC. StoreD. Park73. 选择题：What is the sound a cat makes?A. BarkB. MeowC. RoarD. Quack答案:B74. 选择题：How many months have 31 days?A. FiveB. SixC. SevenD. Eight答案：C75. 选择题：What is the name of the famous American landmark known for its historic significance?A. Lincoln MemorialB. Statue of LibertyC. Mount RushmoreD. All of the above答案: D. All of the above76. 填空题：The __________ (历史的启示) guides our future.77. 听力题：The ________ (cello) is a musical instrument.78. 听力题：A ____ is a fascinating creature that can change color.The process of ______ involves the gradual breakdown of rocks.80. 填空题：The _____ (香葱) adds flavor to dishes.81. 选择题：What is the name of the famous American singer known for "I Want to Dance with Somebody"?A. Whitney HoustonB. Mariah CareyC. Janet JacksonD. Celine Dion答案: A82. 选择题：What do you call a story that teaches a lesson or moral?A. FableB. NovelC. BiographyD. Play答案: A83. 填空题：I want to _______ (探索) new places.84. 听力题：The weather is _____ (sunny/cloudy) today.85. 听力题：Dolphins are known for their ______ behavior.86. 填空题：I enjoy visiting ______ during summer break.87. 填空题：The _______ (Lewis and Clark Expedition) explored the western territories of the US.88. 填空题：A __________ (无机化合物) does not primarily contain carbon.89. 填空题：A ______ (水培) system allows plants to grow in water.90. 选择题：What is the term for a moon that orbits a planet in the opposite direction of its rotation?A. Retrograde MoonB. Anomalous MoonC. Irregular MoonD. Regular Moon91. 听力题：The chemical formula for sodium thiosulfate is _______.92. 填空题：I watched a _______ (小蛇) slither by.93. 选择题：What do you call the act of learning about something?A. StudyingB. TeachingC. ExploringD. Researching答案: A94. Empire was known for its strong _______. (军队) 填空题：The Rose95. 填空题：I enjoy studying different cultures and their ________ (传统).96. 填空题：A puppy loves to ______ (跳跃) around.97. 填空题：The _______ (Silk Road) was a trade route that connected the East and West.98. 听力题：The _______ can grow in sandy soil.99. 选择题：What is the name of the famous tree-dwelling marsupial from Australia?A. KoalaB. KangarooC. WallabyD. Wombat100. 填空题：The __________ (历史的传递) conveys wisdom.。

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38IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS—PART A: SYSTEMS AND HUMANS, VOL. 34, NO. 1, JANUARY 2004Elementary Siphons of Petri Nets and Their Application to Deadlock Prevention in Flexible Manufacturing SystemsZhiWu Li and MengChu Zhou, Fellow, IEEEAbstract—A variety of important Petri net-based methods to prevent deadlocks arising in flexible manufacturing systems (FMS) are to add some control places and related arcs to strict minimal siphons (SMS) such that no siphon can be emptied. Since the number of minimal siphons grows in general exponentially with respect to a Petri net size, their disadvantages lie in that they often add too many additional places to the net, thereby making the resulting net model much more complex than the original one. This paper explores ways to minimize the new additions of places while achieving the same control purpose. It proposes for the first time the concept of elementary siphons that are a special class of siphons. The set of elementary siphons in a Petri net is generally a proper subset of the set of all SMS. Its smaller cardinality becomes evident in large Petri net models. This paper proves that by adding a control place for each elementary siphon to make sure that it is marked, deadlock can be successfully prevented. Compared with the existing methods, the new method requires a much smaller number of control places and, therefore, is suitable for large-scale Petri nets. An FMS example is used to illustrate the proposed concepts and policy, and show the significant advantage over the previous methods. Index Terms—Deadlock prevention, flexible manufacturing systems, Petri nets, siphons.I. INTRODUCTIONAFLEXIBLE manufacturing system (FMS) is a computer controlled configuration where different operations can be executed. Generally it consists of various kinds of general-purpose workstations, a palletized and programmable material handling system, and other types of resources such as fixtures and buffers. To effectively operate an FMS and meet its production objectives, the use of limited resources among various competing jobs has to be carefully controlled or coordinated. Since various jobs are concurrently processed and these jobs have to share some common resources, deadlocks may occur in an FMS during its operation, which are undesirable phenomena inManuscript received September 1, 2002; revised April 28, 2003. This work was supported in part by the National Defense Research Foundation of China, Youth Scientific Research Workstation in Xidian University, and the New Jersey Commission on Science and Technology. This paper was recommended by Guest Editors M. D. Jeng and M. P. Fanti. Z. Li is with the School of Electro-Mechanical Engineering, Xidian University, Xi’an, 710071 China. He is also with Systems Control Group, Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, M5S 3G4 Canada (e-mail: zhwli@). M. Zhou is with the Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102 USA and also with Institute of Automation, Chinese Academy of Sciences, Beijing 100080, China (e-mail: zhou@). Digital Object Identifier 10.1109/TSMCA.2003.820576a highly automated FMS. This paper focuses on the deadlock problems in such FMS. One way of dealing with deadlock problems is to model an FMS with Petri nets. Petri nets [1], [2] have a simple mathematical representation useful for the analysis and design of discrete event systems including FMS. To cope with deadlocks based on a Petri net formalism, four different approaches are developed. The first one is called deadlock avoidance [3], [8]–[11], [24]. When adopted, some constraints are imposed on the system evolutions such that it is always possible to ensure that the processing of each job can be finished. The second one is the deadlock detection and recovery. It permits deadlock to occur and is able to detect it. Once detected, some recovery actions can be manually or automatically taken [3], [12], [13]. This approach is suitable when deadlocks are rare in a system and a detection and recovery procedure is in place. The last two belong to deadlock prevention approaches. One is to use a Petri net synthesis approach to build models with desired properties such as deadlock-freeness or liveness. Most synthesis methods use special rules in model construction processes. The applications of these rules ensure that the final models satisfy some desired properties. These techniques are not suitable for general nets, but only some special subclasses, implying special classes of FMS [12], [14]–[16], [25]. The other is to build freely a Petri net model first and then add necessary control to it such that the controlled model is deadlock-free [3]–[7], [22], [26], [27]. Control places and related arcs are often used to achieve such purpose [5]–[7], [22], [26], [27]. Ezpeleta et al. [6] defined a subclass of the ordinary and conservative Petri nets called system of simple sequential processes with resources ( ) and required the target Petri net to be in that subclass. A control place is added to every SMS such that liveness can be enforced. The method is simple and guarantees a success. However, too many control places and arcs have to be added, leading to a much more complex Petri net than the originally built one. In fact, the number of places added is equal to the number of SMS in the target net and the number of arcs added is generally much larger than that of places added, particularly for large-scale Petri nets. Partially enlightened by the work in [17], Iordache et al. [7] proposed an iterative control policy of liveness enforcement for Petri nets. It is applicable to an arbitrary Petri net structure. However, a hard nut remains to crack that this method will not work for complex or large Petri net structures. The real cause behind this is simple since there are usually too many SMS in a1083-4427/04$20.00 © 2004 IEEELI AND ZHOU: ELEMENTARY SIPHONS OF PETRI NETS AND THEIR APPLICATION39large-size Petri net. At every iterative step, control places have to be added. Hence, the number of SMS may likely spiral up, which finally becomes unmanageable as the iterations proceed. The shortcoming of the existing methods that need introduce successive control places when the number of SMS is large in a Petri net motivates this particular research. In this paper, to the best of the authors’ knowledge, we first propose the concept of elementary siphons in Petri nets, which are a special class of SMS. We classify SMS in a Petri nets into two categories: elementary siphons and redundant siphons. By making the elementary siphons invariant-controlled in a Petri net, we prove that, under some conditions, its redundant siphons can be always marked. That means when these conditions are satisfied, no control place is needed to add in order to guarantee that redundant siphons can be always marked. For a class of Petri nets, [6], which we target in this paper, we show that the complementary set of a redundant siphon is the union of the complementary siphons of its elementary siphons. This leads to the conditions under which a redundant siphon are always marked when its elementary siphons are controlled by the method [6] which prefrom being unmarked. This vents an SMS in a marked allows us to develop a deadlock prevention algorithm for this particular class of Petri nets. The rest of this paper is organized as follows. Section II reviews basic Petri net definitions and properties that are used throughout the paper. Section III introduces the class of Petri net models as well as an approach that renders an SMS in always be marked by adding a control place without an generating new SMS [6]. Section IV proposes the concepts of elementary and redundant siphons in Petri nets. An invariantbased control method for elementary siphons and the controlability conditions of redundant siphons are presented in Section V. Section VI consist of a control method for redundant siphons, which is based on the concept of complementary sets . In Section VII we develop a deadlock preof SMS in an . Section VIII introduces an FMS vention algorithm for an example to illustrate the applications of the proposed concepts and policy. Section IX presents some discussions about this research work. Further research topics are concluded in Section X. II. BASIC PETRI NET DEFINITIONS AND PROPERTIES Throughout the paper, the following notation is used. where and are A Petri net is a 3-tuple finite, nonempty, and disjoint sets. is the set of places and is the set of transitions. is called the flow relation or the set of directed arcs. be a Petri net or a net for simplicity. Let is defined as The preset of a node . The postset of a node is defined . The preset (postset) of a set as is defined as the union of the presets (postsets) of its elements. A marking of is mapping , where .( ) is called a net system or a marked net. indicates the number of tokens on under . is marked by iff . A subset is marked by iff at least one place in is marked by . The sum of tokens on all , where . places in is denoted byA transitionis enabled under , in symbols , iff holds. If holds the transition may , denoted by , fire, resulting in a new marking with if ; if ; and otherwise , for all . , in symThe set of all markings reachable from a marking , is the smallest set in which bols and if both and hold. Let ( ) be a net system and . A tranis live under iff , sition holds. is dead under iff holds. ( ) is deadlock-free iff , holds. ( ) is live iff is .( ) is bounded iff , live under , holds. is pure iff . We assume that in the following all Petri nets are bounded and pure since the Petri net models of many physical systems are bounded and a nonpure net can be transformed into a pure one while keeping its dynamic behavior. indexed by A -vector is a column vector and a -vector is a column vector indexed by , is where is the set of integers. The incidence matrix of a matrix indexed by and such that if ; if ; and for all and . We denote otherwise and column vectors where every entry equals 0(1) by 0(1). are the transposed versions of a vector and a matrix , and respectively. is a -invariant (place invariant) iff hold. is a -invariant (transition invariant) and hold. iff is called the support of .A -invariant is minimal if there does not exist a -invariant such that . is a siphon iff holds. A A nonempty set siphon is minimal iff there is no siphon contained in as a proper subset. A minimal siphon is called strict if it does not contain the support of any -invariant of a net . As mentioned above, strict minimal siphons are denoted as SMS for short. The solution for SMS in a Petri net is theoretically well-developed [20], [21]. First find siphons, minimal siphons, and -invariants in a Petri net and then exclude the minimal siphons which contain the support of a -invariant. Let ( ) be a net system with , be a -invariant, and be a siphon of . Siphon is controlled iff and for by -invariant under hold, or equivalently, and all [17]. Such a siphon is also called an invariant-controlled siphon [23]. be a net. generates the Let , where subnet , and . A string is iff , called a path of , . A simple path is a path where and ). A whose nodes are all different (except, perhaps, path is called a circuit iff it is a simple path and . Petri net is called a state machine iff , .40IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS—PART A: SYSTEMS AND HUMANS, VOL. 34, NO. 1, JANUARY 2004Let ( ) be a marked Petri net. The following properties are known [23], [28]. Property 1: The linear combination of and is a –invariant of if both and are –invariants. Furtherthen given an initial marking more, if is a –invariant of , , . be a siphon of . If is controlled Property 2: Let by a –invariant under , cannot be emptied, i.e., , is marked under . ) is dead, the set of all unmarked places Property 3: If ( can be emptied, forms a siphon. If no minimal siphon in ( ) is deadlock-free.III. CLASS OF THEPETRI NET MODELSIn this paper we shall apply our deadlock control method to which, firstly proposed in [6] and used to model a class of FMS, is a subclass of ordinary and conservative Petri nets called ). system of simple sequential processes with resources ( model and its properties in In this section we introduce detail to make this paper self-contained. ) is a Petri Definition 1: A Simple Sequential Process ( , where: 1) ( is called net ( is called a process idle place); an operation place), 2) is a strongly connected state machine; and 3) every circuit contains place . of Definition 2: A Simple Sequential Process with Resources ) is a Petri net such that 1) ( the subnet generated by is an ; 2) ( is called a resource or a resource place in a net formalism) ; 3) , , , and , ; 4) the two following statements are verified: a) , and , ; and 5) ; b) , , the operation places that use , For is called the set of holders of . We will denote as , where is a set of resources. be an . Definition 3: Let is called an acceptable initial marking An initial marking for iff: 1) ; 2) , ; and 3) , . The couple ( ) is called an (acceptable) marked . In the sequel, when we talk about a marked , , we will refer to with an acceptable marking . and denote We introduce now, recursively, the definition of a system of , that is called . , , is defined recurDefinition 4: A System of is an . 2) Let sively as follows: 1) An , be two such that , , and (in and are two composable ); which case we say that resulting from the comthen, the net and via (denoted as ) defined as position of follows: 1) , 2) , 3) ; ; and 5) is also an . 4)are The meaning of the previous definition is clear: two composable when they share a set of resources, and then, their composition is defined as the composition of the two nets via a set of common places. We introduce now the definition of an iff one of the two following statements acceptable marked ) is an acceptably marked ; 2) is true: 1) ( , such that ( ) is an acceptably marked and a) , , ; b) , , ; and c) , max . we In the sequel, when talking about a marked refer to an with an acceptable initial marking. Adhas the following -invariant property: ditionally, , , and are . We can see that the the supports of -invariants of an support of any -invariant in are initially marked. Or, a place set in which no element is initially marked is not possibly . We call this -invariant the support of a -invariant in , which will be used later on. In the following property of to represent of th . we use be an . (1) Let be Definition 5: Let a circuit of , and let and be two nodes of . We say that is previous to in iff there exists a path in from to , the length (given a circuit , we denote the set of nodes in ) of which is greater than 1 and it, and the length . (2) Let which does not pass . This fact is denoted by and be two nodes of . We say that is previous to in iff there exists a circuit such that . This fact is denoted . (3) Let and be a node and a set of as iff there exists a node nodes, respectively. Then such that . iff there exists a node such that . Definition 6: Let be an . is used to denote the set of SMS in . Given , where , , , denotes the following set of places: , while , . For a given siphon , is the set of holders, corresponding to resources in , which do is called ’s complementary set. not belong to . Property 4: Let be an SMS in an , where . Then , , and , . Proof: By Definition 6, . While, , , due to the definitions of an . This trivially leads to the truth of this property. Property 4 shows that for a given SMS in an , where , , the number of the appear, and . ances of is unit in , is Property 5: For a given SMS in an the support of a -invariant of . Proof: Trivial from Definition 6 and Property 4. Definition 7: Let be an and be the set of SMS in . ( ) is a mapping where . is a mapping where . , , , .LI AND ZHOU: ELEMENTARY SIPHONS OF PETRI NETS AND THEIR APPLICATION41) be a marked . The net is the controlled system of ( ) iff 1) is the set of additional control places such that there exists a bijecinto it; 2) tive mapping from where , , andDefinition 8: Let (IV. ELEMENTARY SIPHONS IN PETRI NETS In this section, we define elementary and redundant siphons in a Petri net. be a subset of places of . -vector Definition 9: Let is called the characteristic -vector of iff : ; otherwise . be a subset of places of and Definition 10: Let be the characteristic -vector of . is called the characteristic -vector of if . Property 6: The characteristic -vector of the support of a -invariant is 0, where the maximum absolute value of any element in the -invariant is unit. Proof: The characteristic -vector of the support of -invariant is exactly itself. According to the definitions of -invariants and characteristic -vectors, this property apparently holds. In Fig. 1, let . Therefore one has . We have since is the support of a -invariant of . Property 7: Let be a place subset of net and be its characteristic -vector. Sets , , and are the sets of transitions whose firings increase, maintain and decrease the number of tokens in , respectively. Proof: We prove the case of as follows. , let , , and . Clearly, and , , cannot be empty simultaneously since is not empty. and According to the firing rules of Petri nets, firing will increase , decrease in , but not change in the number of tokens in . By Definition 10, if then one has . Therefore, , the token increment in is ( ) by firing . The other two cases can be similarly proved. Property 7 states the meaning of the characteristic -vector in of a subset of places. For instance, let Fig. 1. One can see that firing decreases the number of tokens in by one and maintains it in , , and . Hence, firing decreases the number of tokens in by one. It is so because , where . One can easily check other cases. In the following, we use to denote the set of SMS of a net and denote the characteristic -vector of siphon , where . , if Definition 11: such that holds, where , then is called an elementary siphon of . to denote the set of elementary siphons in a net We use . be a siphon in a net and Definition 12: Let be its elementary siphons. is called a , and if strict redundant siphon w.r.t. holds, where .is defined as follows: (a) , ; (b) , , . where The approach proposed in [6] is to add a control place for each SMS such that it can never be emptied without generating new . In this paper SMS. Note that in [6] for every SMS , siphon control depth variable, which indicates the we call least number of tokens that siphon can hold. Obviously is equal to or greater than 1 to achieve our control purpose. In the following we will prove that when the method in [6] is applied with , all SMS in the original to an net system ( ) are also controlled. Here a controlled SMS means it can never be emptied. ) be the controlled system Proposition 1: [6], Let ( ,( ), and let . of a marked Then, the following invariant relation is verified: . Proposition 2: Let ( ) be the controlled system of a ( ), where , and marked be a reachable marking. Then , . Proof: Let . Since is , we the support of a -invariant (weighted by 1) and . can conclude that Considering the invariant relation in Proposition 1 and this , we have that last result, if and then, . Therefore, , which is obviously impossible. Proposition 3: Let ( ) be the controlled system of a ( ), where , , marked , and . Then, is not dead for in ). ( , , which Proof: [6] proposed a proof when . However, , the relation: ensures also ensures that holds. Similarly to the proof of Lemma VI.4 in [6], this proposition is true. Proposition 4: [6], Let ( ) be the controlled system ( ). , , of an ,( ) is live. In conclusion, the method proposed in [6] guarantees that all are controlled and hence the controlled net SMS in an system is live. In this paper one can see that we only use eland we can ementary siphons to control all SMS in an likewise ensure that the controlled net system is live.and 3)42IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS—PART A: SYSTEMS AND HUMANS, VOL. 34, NO. 1, JANUARY 2004Fig. 1.Petri net (N ; M ).For example, there are three SMS in the net shown , in Fig. 1, which are , and . One can obtain that , and . Hence, , , and . We can see that . Thus is a strict redundant siphon. be a siphon of a net , let Definition 13: Let be its elementary siphons. w.r.t. is called a slack redundant SMS , and ifholds, where . is a redundant siphon w.r.t. elementary siphons If , and , we say that , and are the elementary siphons of . In the following, the set of re. Obviously, one can get dundant siphons is denoted by . In Fig. 1, . Obviously, and are the , and . elementary siphons of , is a strict redundant siphon and there is no slack redundant siphon in Fig. 1. By the meaning of the characteristic -vector of a siphon and Definitions 12 or 13, we can see that the change of token count in a redundant siphon is strongly related to the token flow in its elementary siphons. For example, suppose is a strict redundant siphon w.r.t. and in some net that has , four transitions , , , and , where , and . It is clear that and and firing firing decreases the number of tokens in decreases the number of tokens in and . Suppose that , , , and at some initial marking. Furthermore, assume that we can find some way to guarantee that the maximal difference between the number of , times that fires and the number of times that fires is which ensures that cannot be cleared of tokens, and the maximal difference between the number of times that fires and the , which ensures that number of times that fires is cannot be cleared of tokens. If holds, obviously redundant siphon can never become unmarked. In other words, redundant siphon will always be marked proand are always guaranteed to be marked. In vided that Sections V and VI, we will present the formal conditions under which a redundant siphon can never be emptied by controlling its elementary siphons not to be emptied. be a net with , Definition 14: Let and we assume has SMS, , and , , , . Let be the character-vector of siphon , . We istic and define is called the characteristic -vector matrix of the siphons of . be a net and be the characteristic Proposition 5: Let -vector matrix of the siphons of it. The number of elementary siphons in is the rank of . Proof: Assume that has siphons and elementary because the set of elementary siphons siphons. Note that in a net is a subset of siphons. When there is no redundant siphon . Otherwise, there are redundant siphons in a net, in . By Definitions 12 and 13, ( can be linearly represented by ( . According to the definition of the rank of a matrix, we have the rank of is . Due to Proposition 5, it is easy to find elementary siphons in given all siphons. First, we construct a Petri net system and then . Then linearly independent vectors can matrix be found in . Finally, the siphons that correspond to these linearly independent vectors are the elementary siphons in the . net system for the Petri net in Fig. 1 is as follows. EvFor example, is 2 since the third row can be linearly idently, the rank of represented by the first and second rows. Therefore the siphons which correspond to the first and second rows are elementary siphons.V. CONTROL OF ELEMENTARY AND REDUNDANT SIPHONS It is well known that a Petri net is deadlock-free if no siphons can be emptied. Also it is a sufficient condition for the liveness of some subclasses of Petri nets. In the sequel, we categorize SMS in a net into two classes, redundant and elementary. The results obtained in this section show that under some conditions redundant siphons and hence all SMS in a net cannot be emptied if we can prevent the elementary siphons from being emptied. That means we do not need to consider all SMS in a net when we try to ensure that no siphon in a net can be emptied. In theLI AND ZHOU: ELEMENTARY SIPHONS OF PETRI NETS AND THEIR APPLICATION43rest of this paper, we say a siphon in a net system is controlled when it is always marked at any reachable marking of the net system. First we employ an established method in supervisory control of Petri nets to prevent an SMS from being emptied, which is based on place invariants [18]. Proposition 6: Let be an SMS of a net system ( ), where . to to make -vector Add a control place be a -in), where , variant of the new net system ( ; , ; ; , ; and , where is a row vector due to the addition of place . Let where . Then is an invariant-controlled SMS and hence always marked at any ). reachable marking of ( is a -invariant of and Proof: . Note that . According to Property 2, is an invariant-controlled siphon. To make a siphon be always marked in a net system, we have to keep at least one token staying at at any reachable marking of the net system. Suppose some way is found which controls never to be emptied and the least number of tokens staying at is denoted as, say, . As mentioned above, is called the siphon control depth variable. It is obvious the larger is, the more behavior of the modeled system will be restricted, which, in Petri net formalism, means more reachable states will be forbidden. Therefore, let the siphon control depth variable be 1 whenever possible. After is extended by , incidence matrix is ex. Note that tended by one row, denoted by and is a -invariant of . We have and . Furthermore we have and . And we can is . see that and For example, are elementary siphons in Fig. 1. We and to control and , add two control places ) is respectively. The new net system denoted by ( shown in Fig. 2. Hence, we have , . It is easy to check that and can where never be emptied. Proposition 6 provides a way to prevent an SMS from being emptied. The next theorem shows a strict redundant SMS can be invariant-controlled through making its elementary siphons invariant-controlled. )be a net system and , Theorem 1: Let ( and be its SMS. Assume that is a strict redundant SMS , and , where w.r.t. elementary siphons . is controlled if (1) is , and extended by additional control places such that , and are invariant-controlled and (2) . is an invariant-conProof: We will demonstrate that trolled siphon.Fig. 2.N is added with two control places.be the characteristic -vector of siphon , . The new net system with additional con, and is denoted by ( ). Oband . Note that and . Hence,Let trol places viously,Accordingdefinition of -invariants, is a -invariant of net . is always marked under , Next, we prove that . By Property 1 of Petri nets,totheNote that. Therefore we haveDue to have, we is. That is to say, , . Hence, an invariant-controlled siphon due to Property 2.44IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS—PART A: SYSTEMS AND HUMANS, VOL. 34, NO. 1, JANUARY 2004Note that it is important to determine when elementary siphons are employed to prevent a strict redundant siphon from being emptied. On the one hand, a small for each elementary siphon is desired. On the other hand, two prior conditions , which are (1) , must be satisfied for and (2) . is a redundant siphon and and are In Fig. 1, its elementary siphons. We can see that and . Let , we have . Thus can and are controlled via adding two never be emptied after control places, as shown in Fig. 2. Generally, only Petri nets with complex structures contain slack redundant siphons. There is no such a siphon in the nets shown in Figs. 1 and 2. We have the following conclusion for the control of a slack elementary siphon. Theorem 2: Let ( ) be a net system and , and be SMS . is a slack redundant SMS w.r.t. elementary siphons of , and , where, to make render the following relation true:hold we have toDue to the fact that max SMS, we can see thatsince ,, is an whenholds. After the proof, an alternative is given to facilitate the understanding of this conclusion. By the implication of the characteristic -vector of a siphon andis controlled if (1) is extended by places , and such that , and are invariant-controlled and (2) . ) denote the new net system with Proof: Let ( additional control places, be the characteristic -vector be the characteristic -vector of , where of , and . (See equation at bottom of the page.) is Hence a -invariant of . , we have . Thereforewe can see that the number of tokens held by may increase increases (de(decrease) as the number of tokens held by . However, the number of tokens creases), held by may decrease (increase) as the number of tokens held ( ) increases (decreases). by ), the most imporHence, for ( tant thing that we concern is not the token decrement but rather to be always marked. the token increment in it if we desire By the definition and properties of siphons, we know that the number of tokens staying at a siphon at any reachable marking must be less than or at most equal to the initial number of tokens held by it. As a whole, the token input and output for siphon , ) will not decrease the number ( of tokens in . This leads to the following corollary. be a slack redundant siphon w.r.t. Corollary 1: Let in a net system andThen whether can be emptied only depends on siphons , and whatever control policy is employed. From the viewpoint of preventing a redundant siphon from being cleared of tokens, there is no difference between strict and。