常用it作形式主语的句型结构

常用 it 作形式主语的句型结构◊It + be +形容词+ that-从句可用于此句型的形容词有 : wonderful, true，good，right，wrong，(un)important ，useless，surprising， clear, unusual, lucky, certain, necessary等。

女口：①It isquite certain that hewill be at the meeting.②It is surprising that he came late to school this morning.③It isimportant that we(should) study hard注意：该句型中的形容词是(un) important, necessary等时，从句应为(should )+动词原形。

◊It + be + -ed 分词 + that-从句适用该句型的过去分词主要有：said,reported, announced,hoped,thought, told, believed, expected, decided, suggested,known 等。

如：①It ishoped thatonedaytheywill haveenoughanimalsto setthem free②It is well known that the earth goes around the sun.③It is suggested that the sports meeting (should ) be put off until next week.注意：该句型的过去分词是suggested时，从句应为(should )+动词原形。

◊It + be + 名词 + that-从句适用该句型的名词 (词组) 有：apity, anhonor, agood thing, afact, asurprise, goodnews, one's duty 等。

如：① It isapity (that)you missedthesportsmeetinglastweek.② It isafactthatEnglish isbeingacceptedasaninternational language.◊It ＋seem／ appear／ happen 的适当形式＋ that 从句。

该句型常可以转换成含不定式的简单句。

如：①It seemsthat thereisabig wastepipecomingdown from the town.T There seemsto be a big waste pipe coming down from the town.②He appearedto becalm,but insidehisheartwasbeatingwildly with fear.t It appearedthathewascalm,butinsidehisheartwasbeatingwildly with fear.◊It does n't matter ( It 'no won der; It does n 'make much differe nee 等)＋ when/ where/ which/ whether 等从句。

如：①Does it matterif hecan'tfinish thejob ontime?②Theyareallclassmates. It isnowonderthey should help eachother with their studies.◊It + be+ adj./ n. (for sb./ ofsb.)+ todosth. 该句型中的形容词通常是表示事物的特点或特征的如 difficult , hard, easy, impossible, necessary, important 等,此时用 fo r ；或表示人的性格特征或特点的如nice, good, bad, kind, silly, foolish, wise, clever, careless, rude, brave, cruel, careful, grateful等，这时要用 of。

如：① It is foolish of you to give up such a good chance.② It is necessary for college students to master at least a foreign languageIt 作形式主语常见句型动词不定式，动名词或主语从句作主语时，通常把它们放在谓语动词前，而用 it 作形式主语，放到句首，常见句型有：1. It + be + 形容词 +主语从句，如：It is uncertain whether he can come to Jen'nys birthday party or not.2. It + be + 名词词组 + 主语从句，这类名词有： a fact, a pity, a shame, an hono，ura question等，如：It's a pity that you missed the exciting football match.It remains a question whether he will come or not.3. It + be + 过去分词 + 主语从句，这类过去分词有： announced, believed, expected, hoped, decided, reported, said, sho等n 如:It is reported that 16 people were killed in the earthquake.It is not decided who will give the operation to the patient.4. It +不及物动词（seem,即pear, happe等） +主语从句，这类不及物动词有：appear, happe n, seei等, 如:It seemed that he didn't tell the truth.It happened that I was out when he called.5. It + be + 形容词 + for sb.)+ 动词不定式这类句型常用形容词 easy, difficult, hard, important, possibl, wise等作表语，有时候为了强调不定式动作的执行者，常在不定式前加for sb,如：It's necessary for the young to master two foreign language.It is unwise to give the children whatever they want.这类形容词有： easy, difficult, hard, important, possib,lewise6. It + be + 形容词 + of sb. + 动词不定式,这类形容词常是表示心理品质 ,性格特征的形容词,如： kind, nice stupid, clever, foolish, polite, impolite, silly, selfish, con siderate等。

某人和这些形容词可以构成主系表结构。

如：It's very kind of you to help me with the work.=You are kind to help me.It seemed selfish of him not to share his dictionary with others.=He seemed selfish not to share his dictionary with others.7. It + be + 名词词组 + 动词不定式,如：It is not a good habit to stay up too late.8. It + be + 名词或形容词 + 动名词,这类名词和形容词常常是： good, no good,no use, a waste of, useless, sen se等，女口：It's a waste of time talking to her any more.It is no use arguing about the matter with him.9. It + take ( sb. )+时间(金钱)+动词不定式，如：It took the workers almost three years to finish building the dam.It will take a whole day to get to the top of the mountain on foot.实战演练：1. It is gen erally con sidered un wise to give a child ___ he or shewa nts. (NMET 1997)A. howeverB. whateverC.whichever D. whe never2. I n fact ____________ is a hard job for the police to keep order in an importa ntfootball match. (2001 上海)A. thisB. thatC.there D. it3. _________________ is a fact that English is being accepted as an international Ian guage. (NMET1995)A. every oneB. thisC.her D. it 5. ________ will take you a lot of time to find him in the crowd. A. ItB. IC. WeD. They 6. It is no usehisthere, the situati on is hopeless now. A. to go B. to be going C. going D. hav ing gone7. It is n ever too late to lear n, ?A. is itB. is n' t itC. does itD. doesn' t it8. ___________ is known to all thaShe nzhou VI Laun ched Successfully.A. AsB. WhatC. ItD. That 9. _______ is reported in the n ewspapethe Earthquake in east Chi na's Jia ngxi Provincekilled 13 peopleThat D. It 4. Isn ecessary to take off our shoes whe n we en ter the lab? A. ThereB. ThisC.(MET88)A. ItB. AsC.That D. What10. __________ certain that his invention will make peop'les life convenient.A. That'sB. This isC. It'sD. What's11. ________ t hat there is another football match on the air this evening.A. It saysB. It was saidC. It is saidD. What was said12. _________ t hat their daughter got an opportunity to study abroad.A. It's a exciting newsB. This is an exciting newsC. This is exiting newsD. It's exciting news 参考答案：1——5 BDDDA 6—— 10CACAC 11——12CD一、主语从句的概念与类型主语从句在复合句中作主句的主语，引导主语从句的词有从属连词 that, whether以及连接代词who, what, which, whoever, whatever, whichever和连接副词 when, where, why, how等.例女口：That she was chosen made us very hapj她当选了使我们很高兴 .What caused the accident is a complete myste是什么导致了这次事故还完全是一个谜 .Whether she will come or not is still a questio n 她是否来还是一个问题 .Which team will win the match is still unknown. 哪个队会赢得这场比赛还不知道 .When they will start has not been decided yet他们何时出发还没决定 .注意:上述例句中的主语从句都是放在句首，但有时为了使句子结构平衡，避免"头重脚轻",常用it作形式主语 ,而把从句放在后面 .例如 :It is a pity that she has made such a mistake.犯了这样一个错误，真是遗憾.It depends on the climate whether they are going shopping today. 们是否今天去购物还得看天气情况.这样就构成了下面一些常用句型 :1) It is + adj. / n. + 从句It is a pity/shame that...遗憾的是It is possible that..很可能It is unlikely that...不可能2) It + 不及物动词 +从句It seems/appears that..似乎It happened that..碰巧 .3) It + be +过去分词 +从句It is said that..据说It is known to all that…众所周知It is reported that...据报道It is believed that..据信 ............ ；人们相信It is suggested that.有人建议It must be pointed out that...必须指出It is believed that at least a score of buildings were damaged or destroye据信，至少有二十座楼房遭至U破坏或彻底毁掉 .It is suggested that the meeting should be put off有人建议会议延期召开It's reported that three people were killed in the accident and five were hurt badly据报道，事故中三人丧生，五人重伤.It is known to all that Taiwan is an inseparable part of China众所周知，台湾是中国不可分割的一部分.[巩固练习 ]1. Does ______ matter if he can't finish the job on time?A. thisB. thatC. heD. it2. It worried her a bit _ her hair was turning grey.A. whichB. thatC. ifD. for3. ______ is a fact that English is being accepted as an international language.A. ThereB. ThisC. ThatD. It二、学习主语从句应该注意的几个问题1）引导词 that 与 whatwhat既有引导主语从句的作用，同时又在从句中作句子成分（主语、宾语、表语等）.这时what相当于all that/everything that...,常译成"所的（东西、事情、话等.）";而that只起连接作用，本身无实际意义，在从句中也不担当任何句子成分但that引导的主语从句放在句首时，不能省略that.例如：What is done can't be undone. 谚（语）已成定局，无可挽回 .What we can't get seems better than what we hav我们得不到的东西似乎比已得到的要好That we should work out a plan to deal with the present serious situation is important我们应该制定一项计戈 Ll 来应付目前严峻的形势 ,这一点非常重要 .That a new teacher will come to teach us geography is tru e.位新老师将来教我们地理，这是真的.[巩固练习 ]4. ______ what they told me really true?A. HasB. IsC. DoesD. Have5. It matters little _ a man dies， but ____ matters much is _______ he lives.A. how; what; howB. how; it; howC. why; it; whyD. that; what; that6. ______ she couldn't understand was ______ fewer and fewer students showed interest in her lessons.A. What; whyB. That; whatC. What; becauseD. Why; that7. It is pretty well understood _ controls the flow of carbon dioxide in and out the atmosphere today.A. thatB. whenC. whatD. how8. ______ fashion differs from country to country may reflect the cultural differences from one aspect.A. WhatB. ThatC. ThisD. Which9. -What made her parents so angry?- _______ she had failed in the examination.A. AsB. BecauseC. SinceD. That2）引导词 if 和 whetherif 和 whether 引导动词后的宾语从句时一般可通用，但介词后的宾语从句、主语从句（放在句首时）、表语从句常由 whether 引导.例如 :Whether she will go home or not is unknown.她是否回家还不得而知 .=It remains to be decided whether/if we shall raise ducks or geese.但我们不能说 If we shall raise ducks or geese remains to be decided.[巩固练习 ]10. ______ we'll go camping tomorrow depends on the weather.A. IfB. WhetherC. ThatD. Where3）其它引导词连接代词 who, which, whom, whose 有各自的意义 ,起连接作用 ,并在从句中充当语、宾语、表语、定语等连接副词when,where, why, how等有各自的意义，起连接作用，并在从句中充当状语.[巩固练习 ]11. -Do you remember ______ he came?-Yes, I do. He came by car.A. howB. whenC. thatD. if12. I t was a matter of ____ would take the position.A. whoB. whoseC. whomD. whomever13. -I drove to Zhuhai for the air show last week.-Is that ____ you had a few days off?A. whyB. whenC. whatD. where14. I read about it in some book or other, does it matter it was?A. whereB. whatC. howD. which三、语气在 It is necessary / natural / important / strange...+ that-clause 这类句型里，that 所引导的主语从句中谓语动词用"should +原形",表虚似语气例如：It is necessary that the problem should be settled at one这个问题必须马上解决It's strange that he should have gone away without telling u他竟然没向我们说一声就走了，真是奇怪.［巩固练习］15. I t is necessary that a college student at least a foreign language.A. mastersB. should masterC. masteredD. will master四、以it作形式主语的主语从句与强调句型的区别"It be + adj./n. + that-clause"与强调句型均有It be...that..之类的语言标志，但不同的是：①前者中的that从句是主语从句.若删掉其中的It be和that,则剩余部分不论结构还是语意都不能成为一个句子；但若将后者中的It be和that去掉，则剩余部分的结构和语意仍能构成一个完整的句子.②强调句型译为汉语时可加上”正是……"或"就是……"之类的字眼，而主语从句则不可以.请比较下面两个句子：It is surprising that Mary should have won first place 令人惊奇的是玛莉竟然获得了第一名It is Mary that has won first place 正是玛莉得了第一名.第一句话中的It是形式主语，that引导的是主语从句句中的It is和that无法删除，一旦删除句子就不成立第二句是强调句型其中的It is和that可以去掉，因为没有It is和that句子仍然很通顺.Key: 1-5 DBDBA 6-10 ACBDB 11-15 AAADB表语从句1 The traditi onal view is we sleep because our brain is “ programmed ” to make us do so. （2007 上海）A. whenB. whyC. whetherD. that［答案］D［解析］下划线处之后是包含一个原因状语从句的表语从句，如果看不出它是充当整个句子结构的表语从句将难以把握整个句子的意思。