Question

Do you want to know how and why a fall leaf changes color? We first have to

understand what leaves are and what they do.

Leaves are the world’s food factories. Plants take water from the ground through their roots and take CO2 from the air. Plants use sunlight to turn water and CO₂ into glucose(葡萄糖), a kind of sugar. Plants use it as food for energy and growing.

A chemical called “chlorophyll” in the leaves gives plants their green colour. As summer ends and autumn comes, the days get shorter and shorter, and trees “know” to begin getting ready for winter.

During winter, there is not enough sunlight or water. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves.

The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples, sunlight and the cool nights of autumn turn the glucose in the leaves into a red colour. And we can enjoy the beautiful red leaves during autumn.

1.Which should be in the box?

A. air       B. sugar       C. water         D. wind

2.The underlined word “chlorophyll” means __________.

A. 叶绿素     B. 脂肪        C.蛋白质         D.淀粉

3.The leaves turn yellow because they are short of(缺少) __________.

A. water and CO2          B. glucose and energy

C. sunlight and water     D. sunlight and CO2

4.Which of the following is NOT true?

A. When autumn comes, the days get shorter and shorter.

B. During winter trees live on the food they store in summer.

C. During winter some of yellow and orange colors are still in the leaves.

D. Trees begin to stop making food in summer.

5.This passage tells us_____________.

A. the plants can grow well only with the sunlight

B. there are all kinds of plants on the earth

C. not all the colors of the leaves are from chlorophyll

D. maple leaves change the color as other trees

Answer

1.C

2.A

3.C

4.D

5.C

【解析】

试题分析：短文大意： 叶子是世界上的食品加工厂。植物通过自己的根从地面吸取水分，从空气中吸收二氧化碳。植物利用阳光将水和二氧化碳转化为葡萄糖。植物用它作为能源和食物。“叶绿素”给植物的叶子绿颜色。

1.C细节理解题。根据第二段中Plants use sunlight to turn water and CO2 into glucose(葡萄糖), a kind of sugar.可知植物利用阳光将水和二氧化碳转化为一种葡萄糖，所以该选C。

2.A词义猜测题。根据后面的gives plants their green colour可知“chlorophyll”是叶绿素，所以该选A。

3.C细节理解题。根据第四段中During winter, there is not enough sunlight or water. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves.的描述可知叶子变黄是因为缺少阳光和水，所以该选C。

4.D细节理解题。根据生活常识可知在冬天树叶都落啦，所以该选D。

5.描述可知叶绿素使叶子为绿色，但并不是所有的叶子的颜色都来自叶绿素，所以该选C。

考点：科普类阅读。