托福阅读真题+题目+答案：Leaf Shapes

托福阅读真题+题目+答案：Leaf Shapes

Plant leaves absorb sunlight and carbon dioxide for photosynthesis, the process of converting sunlight, carbon dioxide and water into a chemical used for energy. Pores on the leaf absorb the carbon dioxide, but they also allow water to escape in a process called transpiration. The conflicting needs to intercept light and take up carbon dioxide on the one hand, and to conserve water on the other, have resulted in a number of different leaf shapes in different environments.

1.The word “conflicting” in the passage is closest in meaning to

A.continued

B.opposing

C.varying

D.essential

So many factors govern leaf shape that it can be difficult to make sense of what we see. Leaf size and shape vary according to the conditions under which they grow, including day length, temperature, moisture, and nutrition. Leaves growing later in the summer can be progressively more deeply lobed or longer and narrower. It is perhaps not surprising, therefore, that it is sometimes very difficult to identify a tree from a leaf. Sometimes there is so much apparently random variation within a single tree or species that shape seems to have little significance. Despite this wealth of variation due to genetics and growing conditions, a number of generalizations can be made about leaf shape.

2.Why does the author state that “Leaves growing later in the summer can be progressively more deeply lobed or longer and narrower”?

A.To identify the specific shape and size associated with leaves

B.To argue that the importance of leaf shape in the growth process of plants has not been fully recognized

C.To emphasize that leaf size and shape are largely determined by growing conditions

D.To support the claim that a number of generalizations can be made about leaf shape

3.The word “random” in the passage is closest in meaning to

A.uncontrolled

B.significant

C.significant

D.unusual

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