八年级英语植物结构功能单选题50题

八年级英语植物结构功能单选题50题
1. In a desert environment, plants need to have a deep and extensive root system. Which of the following best explains this?
A. To absorb more sunlight
B. To store more water
C. To support the long stem
D. To make more leaves
答案：B。

解析：在沙漠环境中，水分稀缺。

植物拥有深且广泛的根系主要是为了储存更多的水分。

选项A，植物通过叶片吸收阳光，而不是根部。

选项C，支撑长茎不是沙漠植物根系发达的主要原因。

选项D，根系与制造更多叶片没有直接关联，叶片的产生主要与植物的生长和发育等多种因素有关。

2. The stem of a plant can be thick and strong. What is its main function in a windy area?
A. To transport water to the leaves
B. To hold the leaves up high to get more sunlight
C. To prevent the plant from being blown away
D. To store food for the plant
答案：C。

解析：在多风的地区，植物粗壮的茎的主要功能是防止植物被吹走。

选项A，茎运输水分到叶片是茎的一个功能，但不是在多风地区茎粗壮的主要原因。

选项B，茎将叶片举高以获得更多阳光，但这与多风环境下茎粗壮的关系不大。

选项D，茎可以储存食物，
但这不是在这种环境下茎粗壮的主要功能。

3. Some plants have large leaves. What is the possible function of these large leaves?
A. To reduce water loss
B. To increase the surface area for sunlight absorption
C. To protect the roots from damage
D. To make the plant look beautiful
答案：B。

解析：一些植物有大叶子，大叶子的一个可能功能是增加吸收阳光的表面积。

选项A，大叶子通常会增加水分的散失而不是减少。

选项C，叶子无法保护根部免受损害，根部有自己的保护机制。

选项D，使植物看起来漂亮不是叶子结构的主要功能。

4. The roots of a plant grow downwards. What is the main reason for this?
A. Gravity
B. To find more sunlight
C. To avoid being eaten by animals
D. To get closer to other plants
答案：A。

解析：植物的根向下生长的主要原因是重力。

选项B，根部不能寻找阳光，是叶片负责吸收阳光。

选项C，根向下生长不是为了避免被动物吃掉。

选项D，根向下生长与靠近其他植物没有直接关系。

5. In a rainforest, plants often have long and thin stems. This is mainly
because _.
A. They need to compete for sunlight
B. They need to store a lot of water
C. They need to support heavy fruits
D. They need to resist strong winds
答案：A。

解析：在雨林中，植物经常有细长的茎，这主要是因为它们需要竞争阳光。

雨林中树木高大，植物需要细长的茎来长高以获取阳光。

选项B，细长的茎不是为了储存大量水分。

选项C，细长的茎难以支撑沉重的果实。

选项D，细长的茎不利于抵抗强风。

6. The part of a flower that usually becomes the fruit after fertilization is the _.
A. stamen
B. pistil
C. petal
D. sepal
答案：B。

解析：在植物繁殖过程中，雌蕊（pistil）在受精后通常会发育成果实。

雄蕊（（stamen）的作用是产生花粉，与果实的形成没有直接关系，所以A错误。

花瓣（（petal）主要是吸引昆虫等传粉者，不是发育成果实的部分，C错误。

萼片（（sepal）主要起保护花蕾的作用，与形成果实无关，D错误。

7. Which part of a plant contains the embryo of a new plant?
A. The fruit
C. The seed
D. The flower
答案：C。

解析：种子（（seed）包含着新植物的胚，是植物繁殖的重要结构。

果实（（fruit）主要是保护种子并有助于种子传播，不包含胚本身，A错误。

花粉（pollen）是雄性生殖细胞，不是包含胚的结构，B错误。

花朵（（flower）是繁殖器官，但本身不包含新植物的胚，D错误。

8. In the process of plant reproduction, the function of the anther is to _.
A. receive pollen
B. produce pollen
C. protect the ovary
D. develop into a fruit
答案：B。

解析：在植物繁殖中，花药（（anther）的功能是产生花粉。

柱头（stigma）是接收花粉的结构，而不是花药，A错误。

子房（ovary）是被保护的结构，花药没有保护子房的功能，C错误。

花药不会发育成果实，D错误。

9. The colorful part of a flower that helps to attract pollinators is _.
A. the stamen
B. the pistil
C. the petal
答案：C。

解析：花瓣（petal）通常色彩鲜艳，其功能是吸引传粉者，如蜜蜂等昆虫。

雄蕊（（stamen）主要是产生花粉，与吸引传粉者关系不大，A错误。

雌蕊（（pistil）主要参与受精等过程，不是吸引传粉者的主要结构，B错误。

萼片（（sepal）主要起保护作用，不是吸引传粉者的结构，D错误。

10. What is the main function of the ovule in plant reproduction?
A. To produce nectar
B. To develop into a seed
C. To attract bees
D. To support the flower
答案：B。

解析：在植物繁殖中，胚珠（（ovule）的主要功能是发育成种子。

花蜜（（nectar）是由蜜腺产生的，与胚珠无关，A错误。

吸引蜜蜂的主要是花瓣等结构，不是胚珠，C错误。

胚珠没有支撑花朵的功能，D错误。

11. The cell wall in plant cells is very important for the plant. Which of the following statements best describes its influence on the overall function of the plant?
A. It controls the movement of substances in and out of the cell, just like a gate
B. It stores genetic information and determines the characteristics of the plant
C. It provides support and protection, making the plant stand upright
D. It is the main site for photosynthesis in the plant
答案：C。

解析：植物的细胞壁主要作用是提供支持和保护。

细胞壁比较坚硬，就像框架一样，给予植物细胞形状并支撑起整个植物体，使得植物能够直立生长，而A选项描述的是细胞膜的功能，B选项是细胞核的功能，D选项是叶绿体的功能。

12. Chloroplasts play a crucial role in plants. Which option correctly shows their impact on the overall function of the plant?
A. They break down waste materials in the plant
B. They are responsible for transporting water and nutrients throughout the plant
C. They absorb sunlight and convert it into chemical energy through photosynthesis
D. They are involved in cell division to help the plant grow taller
答案：C。

解析：叶绿体含有叶绿素，能够吸收太阳光能，并通过光合作用将二氧化碳和水转化为储存着能量的有机物，这一过程为植物提供了生长、发育等所需的能量，是植物整体功能得以实现的重要基础。

A选项是溶酶体等结构的作用，B选项是导管和筛管等结构的功能，D选项是细胞核等在细胞分裂中的作用与叶绿体无关。

13. In a plant, the vacuole is a large structure. How does it affect the overall function of the plant?
A. It is the place where proteins are made
B. It helps regulate the water content in the plant cell, which affects the turgor pressure and keeps the plant firm
C. It helps the plant to reproduce by producing seeds
D. It is directly involved in the process of gas exchange in the plant
答案：B。

解析：植物细胞中的液泡可以储存大量的水分等物质。

当液泡内充满水分时，会产生膨压，这种膨压能够让植物细胞保持坚挺，从而使整个植物体保持直立等正常形态，进而影响植物的整体功能。

A选项是核糖体的功能，C选项与花、果实等生殖结构有关，D 选项主要是气孔等结构参与气体交换。

14. The nucleus in a plant cell has an important influence on the plant. Which of the following is correct?
A. It provides energy for the cell activities like mitochondria
B. It is mainly in charge of the synthesis of cellulose for the cell wall
C. It contains genetic material that controls the growth, development and characteristics of the plant
D. It is the only place where respiration occurs in the plant cell
答案：C。

解析：细胞核是植物细胞的控制中心，其中包含的遗传物质（（DNA）能够控制植物的生长、发育以及各种特征的遗传。

A 选项中提供能量的是线粒体，B选项纤维素的合成与高尔基体等结构有关，D选项细胞呼吸主要发生在线粒体中。

15. Mitochondria are known as the "powerhouses" of the cell. How do they contribute to the overall function of the plant?
A. They help in the absorption of minerals from the soil
B. They produce ATP through cellular respiration, which provides energy for various life activities of the plant
C. They are responsible for the synthesis of hormones in the plant
D. They are involved in the formation of the root system
答案：B。

解析：线粒体通过细胞呼吸作用将有机物分解并释放能量，产生三磷酸腺苷（（ATP）。

ATP是植物进行各种生命活动（（如生长、繁殖、物质运输等）的直接能量来源，就像一个能量工厂一样为植物的整体功能正常运转提供动力。

A选项与根毛等结构的功能有关，C选项激素的合成与内质网等结构有关，D选项根系统的形成与分生组织等多种结构有关。

16. When a plant lacks water and its leaves start to wilt, which part of the plant is mainly affected in terms of water transportation?
A. The root hairs which are only responsible for absorbing water from the soil but not transporting it upwards
B. The xylem which transports water and minerals from the roots upwards to the rest of the plant
C. The phloem which mainly transports organic nutrients like sugars in both directions not mainly for water transport
D. The stomata on the leaves which are mainly for gas exchange rather than water transportation
答案：B。

解析：植物缺水叶片开始枯萎时，主要是负责将水从
根部向上运输到植物其他部分的结构受到影响。

选项A根毛主要是吸收土壤中的水分而不是向上运输水分。

选项C韧皮部主要是双向运输有机营养物质如糖类，不是主要用于水分运输。

选项D叶片上的气孔主要用于气体交换而不是水分运输，所以正确答案是B。

17. A plant shows signs of nutrient deficiency in its upper parts. Which structure might be having problems in transporting nutrients?
A. The cortex in the root which stores some substances but is not directly involved in upward nutrient transport
B. The endodermis in the root which mainly controls the movement of substances into the vascular system but not the main transporter upwards
C. The phloem which transports organic nutrients from the leaves (where they are made) to other parts of the plant
D. The xylem which is mainly for water and mineral transport from roots to upper parts rather than organic nutrient transport
答案：C。

解析：植物上部出现营养缺乏症状，说明负责将营养物质运输到上部的结构可能有问题。

选项A根的皮层主要是储存一些物质，不直接参与向上的营养物质运输。

选项B根的内皮层主要是控制物质进入维管系统的运动，不是向上运输的主要结构。

选项D木质部主要是进行水和矿物质从根部到上部的运输而不是有机营养物质运输。

而韧皮部是将有机营养物质从制造它们的叶片运输到植物其他部分的结构，所以答案是C。

18. If a plant is not getting enough water, which structure's function is
most crucial to quickly supply water to the leaves?
A. The root cap which protects the tip of the root and has no role in water supply to leaves
B. The pericycle in the root which can give rise to lateral roots but is not directly involved in water supply to leaves
C. The xylem vessels which have a tubular structure and are specialized for rapid upward water transport
D. The companion cells in the phloem which assist in the loading and unloading of organic substances in the phloem not for water transport 答案：C。

解析：当植物得不到足够的水时，需要能够快速向叶片供应水的结构。

选项A根冠是保护根尖的，对向叶片供水没有作用。

选项B根的中柱鞘可以产生侧根，但不直接参与向叶片供水。

选项D韧皮部的伴胞是协助韧皮部中有机物质的装载和卸载的，不是用于水的运输。

而木质部导管具有管状结构，专门用于快速向上运输水，所以答案是C。

19. When a plant has a problem with transporting nutrients in a downward direction, which part is likely to be malfunctioning?
A. The epidermal cells of the root which are mainly for protection and absorption not for nutrient downward transport
B. The xylem tracheids which are mainly for upward water and mineral transport not for downward nutrient transport
C. The phloem sieve tubes which are specialized for transporting
organic nutrients in both directions including downward
D. The mesophyll cells in the leaf which are mainly for photosynthesis not for nutrient transport
答案：C。

解析：当植物在向下运输营养物质方面有问题时，要找与营养物质双向运输（（包括向下运输）有关的结构。

选项A根的表皮细胞主要是保护和吸收作用，不用于营养物质向下运输。

选项B木质部的管胞主要是用于向上运输水和矿物质，不是用于向下运输营养物质。

选项D叶片的叶肉细胞主要是用于光合作用而不是营养物质运输。

而韧皮部的筛管是专门用于包括向下方向的有机营养物质运输的，所以答案是C。

20. A plant is weak and its growth is stunted due to poor nutrient transport. Which structure is most relevant to this situation if it is not working properly?
A. The root nodules which are mainly related to nitrogen fixation not directly to overall nutrient transport
B. The pith in the stem which is mainly for storage and support not the main part for nutrient transport
C. The phloem fibers which mainly provide mechanical support to the phloem not for nutrient transport
D. The phloem which is responsible for transporting nutrients throughout the plant
答案：D。

解析：植物由于营养物质运输不良而虚弱且生长受阻，
如果某个结构不正常工作，要找与整个植物营养物质运输相关的结构。

选项A根瘤主要与固氮有关，不直接与整体营养物质运输相关。

选项B茎的髓主要用于储存和支撑，不是营养物质运输的主要部分。

选项C韧皮部纤维主要为韧皮部提供机械支撑而不是用于营养物质运输。

而韧皮部负责在整个植物中运输营养物质，所以答案是D。

21. When the light intensity is very low, which part of the plant is most affected in the process of photosynthesis?
A. Chloroplast
B. Mitochondria
C. Vacuole
D. Cell wall
答案：A。

解析：在光合作用过程中，叶绿体是进行光合作用的主要场所。

当光照强度很低时，直接影响的是光合作用，而叶绿体是与光合作用紧密相关的结构，光照不足会影响叶绿体中光反应等过程。

线粒体主要与呼吸作用有关，液泡主要储存物质等功能，细胞壁起支持保护作用，它们与光合作用受光照影响的关系不大。

22. High temperature may have a negative impact on the respiration of plants. Which of the following is likely to be the most obvious change?
A. The number of stomata will increase
B. The activity of mitochondria will be inhibited
C. The cell membrane will become thicker
D. The chlorophyll content in chloroplasts will decrease
答案：B。

解析：线粒体是植物进行呼吸作用的主要场所。

高温对植物呼吸作用有负面影响时，线粒体的活性可能会被抑制。

气孔数量增加一般与蒸腾作用等有关，细胞膜变厚与呼吸作用受高温影响关联不大，叶绿体中叶绿素含量减少主要影响光合作用而非呼吸作用。

23. In a dark environment for a long time, what will happen to the function of the grana in the chloroplast?
A. It will work more efficiently
B. It will stop working gradually
C. It will start to perform the function of mitochondria
D. It will only work for respiration
答案：B。

解析：叶绿体中的基粒是进行光合作用光反应的重要结构。

在长时间黑暗环境下，没有光照，光合作用无法进行，基粒的功能会逐渐停止，因为它依赖光照来进行光反应。

基粒不能执行线粒体的功能，也不会只进行呼吸作用，而且没有光照时不会工作得更有效率。

24. If the temperature drops suddenly, which of the following situations is most likely to occur in the plant's photosynthesis?
A. The rate of carbon dioxide uptake by the stomata will increase
B. The conversion of light energy in the chloroplast will be accelerated
C. The activity of enzymes related to photosynthesis will be affected
D. The structure of the cell nucleus will change to adapt to it
答案：C。

解析：温度突然下降时，与光合作用相关的酶的活性会受到影响。

酶的活性对温度比较敏感，温度变化会影响酶促反应的速率，从而影响光合作用。

气孔吸收二氧化碳的速率一般不会因温度突然下降而增加，叶绿体中光能的转换在低温下会受到抑制而不是加速，细胞核结构一般不会为适应温度下降而改变来直接影响光合作用。

25. When plants are in a place with insufficient light for a long time, which of the following statements about the relationship between photosynthesis and respiration is correct?
A. Photosynthesis will be stronger than respiration
B. Respiration will completely stop
C. Photosynthesis will be weaker than respiration
D. Photosynthesis and respiration will be in balance
答案：C。

解析：当植物长时间处于光照不足的地方时，光合作用因为缺乏足够光照，产生有机物的能力会下降，而呼吸作用仍在持续消耗有机物，所以光合作用会比呼吸作用弱。

呼吸作用不会完全停止，在这种情况下光合作用不会比呼吸作用强，也不会处于平衡状态。

26. When a plant is touched, it may fold its leaves. Which part of the plant mainly controls this response?
A. The root
B. The stem
C. The leaf veins
D. The cell membrane
答案：D。

解析：植物受到触碰时折叠叶子是一种应激反应。

植物细胞的细胞膜在感受外界刺激并传导信号方面起主要作用，从而引发植物的这种反应。

而根主要负责吸收水分和养分，茎主要起支撑和运输作用，叶脉主要负责运输和支撑叶片，它们都不是控制这种触碰反应的主要结构。

27. A plant grows sideways when it is placed in a slanting position for
a long time. Which plant structure is mainly responsible for detecting this change in orientation?
A. Chloroplasts
B. Stomata
C. Statoliths in the root cap
D. The cuticle
答案：C。

解析：当植物长时间处于倾斜位置时会侧向生长，这是植物对重力的一种反应。

根冠中的平衡石（statoliths）能够感知重力方向的改变，从而引发植物激素的调节，促使植物生长方向改变。

叶绿体主要与光合作用有关，气孔主要进行气体交换，角质层主要起保护作用，它们与感知重力方向改变无关。

28. Some plants can quickly close their flowers when they are touched. Which part of the plant is most likely to first receive the touch signal?
A. The sepals
B. The petals
C. The pistil
D. The trichomes on the surface
答案：D。

解析：有些植物被触碰时花朵会迅速闭合。

植物表面的毛状体（（trichomes）最有可能首先接收到触碰信号，因为它们在植物的表面，能够最先感知外界的触碰。

萼片主要起保护花蕾的作用，花瓣主要吸引传粉者，雌蕊主要与繁殖有关，它们不是最先接收触碰信号的结构。

29. A plant's roots grow downwards into the soil. Which part of the root is mainly involved in sensing the direction of gravity?
A. The root hairs
B. The cortex of the root
C. The endodermis
D. The root cap
答案：D。

解析：植物的根向下生长入土，根冠（（root cap）主要参与感知重力方向。

根冠中的细胞能够感知重力，从而引导根的向地生长。

根毛主要用于吸收水分和矿物质，根的皮层主要起储存和运输作用，内皮层主要起控制物质进出的作用，它们与感知重力方向关系不大。

30. When a plant is exposed to strong light from one side, it may bend towards the light. Which plant structure is most important in this phototropic response?
A. The xylem
B. The phloem
C. The auxin - producing cells in the shoot tip
D. The epidermal cells
答案：C。

解析：当植物一侧受到强光照射时会向光弯曲。

茎尖产生生长素（（auxin）的细胞在这种向光性反应中最为重要。

生长素在植物体内分布不均匀会导致植物细胞生长速度不同，从而使植物向光弯曲。

木质部主要负责运输水分和矿物质，韧皮部主要运输有机物，表皮细胞主要起保护作用，它们在向光性反应中不是最关键的结构。

31. The _____ in plants is mainly responsible for continuous cell division, which helps the plant grow taller and wider.
A. epidermal tissue
B. parenchyma tissue
C. meristematic tissue
D. sclerenchyma tissue
答案：C。

解析：分生组织（（meristematic tissue）的主要功能是进行细胞分裂，这有助于植物不断长高和长粗。

表皮组织（epidermal tissue）主要起保护作用，薄壁组织（parenchyma tissue）有储存和进行光合作用等功能，厚壁组织（（sclerenchyma tissue）主要起支持作用，所以C选项正确。

32. Which tissue in plants can prevent water loss and protect the plant from being damaged by the outside environment?
A. Ground tissue
B. Vascular tissue
D. Collenchyma tissue
答案：C。

解析：保护组织（（Protective tissue）的功能就是防止植物水分散失并且保护植物免受外界环境的损害。

基本组织（Ground tissue）有多种功能如储存、光合作用等，维管组织（（Vascular tissue）负责运输水分和养分，厚角组织（（Collenchyma tissue）主要起支持作用，所以C正确。

33. The _____ in plants can provide support and strength to the plant body.
A. meristematic tissue
B. epidermal tissue
C. sclerenchyma tissue
D. parenchyma tissue
答案：C。

解析：厚壁组织（sclerenchyma tissue）在植物中能够为植物体提供支撑和力量。

分生组织（meristematic tissue）用于细胞分裂生长，表皮组织（epidermal tissue）用于保护和防止水分散失，薄壁组织（（parenchyma tissue）功能多样但不是主要提供支撑力量的，所以C正确。

34. In a young plant, the _____ is soft and flexible and provides some support as the plant grows.
A. collenchyma tissue
B. sclerenchyma tissue
D. meristematic tissue
答案：A。

解析：在幼嫩植物中，厚角组织（（collenchyma tissue）柔软且有韧性，在植物生长过程中提供一定的支撑作用。

厚壁组织（sclerenchyma tissue）是坚硬的支撑组织，薄壁组织（parenchyma tissue）功能主要不是支撑，分生组织（（meristematic tissue）是用于细胞分裂的，所以A正确。

35. Which of the following tissues in plants is related to the transport of water and nutrients?
A. Epidermal tissue
B. Vascular tissue
C. Protective tissue
D. Ground tissue
答案：B。

解析：维管组织（Vascular tissue）与植物体内水分和养分的运输相关。

表皮组织（Epidermal tissue）主要起保护作用，保护组织（（Protective tissue）也是保护作用，基本组织（（Ground tissue）功能较多但不是运输水和养分的主要组织，所以B正确。

36. In the desert, cacti have very small leaves or spines instead of large leaves. This is mainly because _.
A. small leaves or spines can help cacti lose more water
B. small leaves or spines can reduce water loss
C. small leaves or spines are more beautiful
D. small leaves or spines can attract more insects
答案：B。

解析：在沙漠中，水非常稀缺。

仙人掌有小的叶子或者刺而不是大叶子，主要是因为小叶子或者刺能够减少水分的流失。

大叶子会通过蒸腾作用散失很多水分，而仙人掌这样的结构能更好地适应沙漠干旱的环境，A选项说小叶子或刺会让仙人掌失去更多水是错误的；C选项说小叶子或刺更漂亮不是结构对环境适应的原因；D 选项小叶子或刺吸引更多昆虫也与适应沙漠环境无关。

37. Plants in the rainforest often have broad leaves. What is the main reason?
A. To get more sunlight
B. To store more water
C. To avoid being eaten by animals
D. To resist strong winds
答案：A。

解析：雨林中的植物经常有宽大的叶子，主要原因是为了获取更多的阳光。

雨林中植被茂密，竞争激烈，宽大的叶子可以有更大的面积来接受阳光进行光合作用。

B选项，宽大叶子不是为了储存更多水；C选项，宽大叶子并不能很好地避免被动物吃；D选项，雨林中没有强风的环境特点，不需要宽大叶子来抵御强风。

38. Mangrove plants grow in the coastal wetlands. Their roots are often exposed above the water surface. This is mainly _.
A. for breathing air
B. to catch more fish
C. to support the heavy trunk
D. to prevent being washed away by water
答案：A。

解析：红树林植物生长在沿海湿地，它们的根经常暴露在水面之上，主要是为了呼吸空气。

湿地土壤中氧气含量低，露出水面的根能够获取空气中的氧气来维持生长。

B选项根露出水面不是为了抓鱼；C选项不是为了支撑沉重的树干；D选项防止被水冲走不是主要原因。

39. Alpine plants usually grow low to the ground. What is the advantage of this?
A. To resist the cold climate better
B. To be more easily found by animals
C. To absorb more nutrients from the soil
D. To look more beautiful
答案：A。

解析：高山植物通常贴地生长。

这样做的好处是能够更好地抵御寒冷的气候。

贴近地面可以减少热量的散失，也能在积雪覆盖时有一定的保护作用。

B选项不是为了更容易被动物发现；C选项贴地生长与吸收更多土壤养分没有直接关系；D选项不是为了看起来更漂亮。

40. In the arid grasslands, some plants have deep root systems. The main function is _.
A. to search for water deep underground
B. to fix the soil firmly
C. to compete with other plants for space
D. to make the plant stand more stably
答案：A。

解析：在干旱的草原上，一些植物有很深的根系。

主要功能是寻找地下深处的水。

干旱草原水分缺乏，深根系能够延伸到地下较深的地方获取水源。

B选项虽然深根系有固土作用，但不是主要功能；C选项不是为了与其他植物竞争空间；D选项不是为了让植物站得更稳当。

41. In agricultural production, when we want to improve the yield of fruit trees, we should pay special attention to which part of the plant?
A. Leaves because they are responsible for photosynthesis to produce organic matter for fruit growth
B. Roots because they only absorb water
C. Stems because they are just for supporting the plant
D. Flowers because they have no relation to fruit yield
答案：A。

解析：在农业生产中，提高果树产量时，叶子非常关键，因为叶子负责光合作用制造有机物来供给果实生长。

选项B中说根部只吸收水分是错误的，根部还吸收矿物质等营养成分。

选项C中茎不仅仅是支撑植物，还能运输物质等。

选项D中花朵与果实产量有很大关系，花朵发育成果实。

42. When transplanting seedlings in agriculture, which plant structure should farmers try their best to protect?
A. Root hairs because they are the main part for absorbing water and
B. Petals because they can attract pollinators
C. Buds because they can make the plant look beautiful
D. Branches because they can be used as firewood
答案：A。

解析：在农业中移植幼苗时，根毛是需要尽力保护的结构，因为根毛是吸收水分和养分的主要部位。

选项B花瓣吸引传粉者，但在移植幼苗时不是重点保护对象。

选项C芽不是因为让植物好看而需要保护，并且在移植幼苗时不是重点。

选项D树枝可作柴火，但与移植幼苗时需要保护的结构无关。

43. For better growth of crops, farmers often apply fertilizers around the roots. This is mainly because of which function of the roots?
A. Roots can store fertilizers
B. Roots can secrete substances to dissolve fertilizers
C. Roots are the main organs for absorbing nutrients from the soil
D. Roots can prevent fertilizers from being washed away
答案：C。

解析：农民常在根部周围施肥是因为根部是从土壤中吸收养分的主要器官。

选项A根部不能储存肥料。

选项B根部没有分泌物质溶解肥料这种主要功能。

选项D根部不能防止肥料被冲走，这不是施肥在根部周围的主要原因。

44. In greenhouse cultivation, proper pruning of plant branches is often carried out. The main purpose is related to which plant structure?
A. Leaves because pruning branches can increase the light area of
B. Flowers because pruning branches can make flowers more beautiful
C. Stems because pruning branches can adjust the distribution of plant growth substances in the stems
D. Roots because pruning branches can promote root growth
答案：C。

解析：在温室栽培中，适当修剪植物枝条的主要目的与茎有关，因为修剪枝条可以调整植物生长物质在茎中的分布。

选项A修剪枝条不是为了增加叶子采光面积。

选项B修剪枝条不是为了让花朵更美丽。

选项D修剪枝条不能直接促进根的生长。

45. When farmers intercrop different plants, they need to consider the root systems of different plants. This is mainly because different root systems may have different _.
A. Depths in the soil to fully utilize soil nutrients at different layers
B. Colors which can affect the appearance of the field
C. Shapes which have no practical significance
D. Smells which can drive away pests
答案：A。

解析：农民间作不同植物时需要考虑不同植物的根系，主要是因为不同根系在土壤中的深度可能不同，可以充分利用不同土层的土壤养分。

选项B根系颜色不影响田间外观且不是间作考虑的因素。

选项C根系形状没有实际意义这种说法错误。

选项D根系气味驱害虫不是间作考虑根系的主要原因。