Question

【题目】 We all enjoy the colors of autumn leaves. Did you ever wonder how and why a leaf changes color? Where do the yellows and oranges come from? To answer those questions, 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(叶绿素)” in the leaves gives plants their green color. As summer ends and autumn comes, the days get shorter and shorter, and trees “know” it's time 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 foodmaking 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(枫树), sunlight and the cool nights of autumn turn the glucose in the leaves into a red color. And we can enjoy the beautiful red leaves during autumn.

【1】Which of the following can you put in the box?

sunlight ＋ ＋ CO2 → glucose

A.waterB.sugarC.windD.air

【2】Why do the leaves turn yellow in autumn?

A.Because they are short of glucose and energy.

B.Because they are short of sunlight and water.

C.Because they are short of sunlight and CO2.

D.Because they are short of water and CO2.

【3】Which of the following is NOT true according to the passage?

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

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

C.Trees begin to stop making food and to have a rest in summer.

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

【4】What's the main idea about the passage?

A.It tells us all kinds of plants on the earth.

B.It tells us the plants can grow well with the sunlight.

C.It tells us maple leaves change the color as other trees.

D.It tells not all the colors of the leaves are from chlorophyll.

Answer 1

【答案】

【1】A

【2】B

【3】C

【4】D

【解析】

本篇文章难度适中，主要讲述五颜六色的树叶形成的原因。主要讲述两种原因：一种是叶绿素一种是葡萄糖。

【1】细节理解题。根据Plants use sunlight to turn water and CO2 into glucose(葡萄糖), a kind of sugar“植物利用阳光将水和二氧化碳转化为葡萄糖，一种糖”可知，阳光和水和二氧化碳转化为葡萄糖，故选A。

【2】细节理解题。根据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 foodmaking factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves“在冬天，没有足够的阳光和水。树木在这段时间休息，靠夏天储存的食物生存。他们开始关闭食品制造厂。当绿色的叶绿素从树叶中消失时，我们开始看到黄色和橙色的树叶”可知，因为缺少阳光和水，故选B。

【3】细节理解题。根据As summer ends and autumn comes, the days get shorter and shorter“因为夏天结束秋天到来，白天变得越来越短”，排除A；根据Trees rest during this time and live on the food they store during the summer“树木在这段时间休息，靠夏天储存的食物生存”可知，树靠夏天储存的食物为生，排除B；根据As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves“当绿色的叶绿素从树叶中消失时，我们开始看到黄色和橙色的树叶”可知黄色和橙色的树叶仍在树上，排除D；根据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 foodmaking factories“在冬天，没有足够的阳光和水。树木在这段时间休息，靠夏天储存的食物生存。他们开始关闭食品制造厂”可知，在冬天他们开始停止生产食物并且休息，而不是在夏天，故选C。

【4】推理判断题。根据As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves“当绿色的叶绿素从树叶中消失时，我们开始看到黄色和橙色的树叶”以及The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples(枫树), sunlight and the cool nights of autumn turn the glucose in the leaves into a red color. And we can enjoy the beautiful red leaves during autumn“我们在树叶中看到的明亮的红色和紫色主要是在秋天制造的。在一些树上，像枫树，阳光和秋天凉爽的夜晚把树叶中的葡萄糖变成红色。我们可以在秋天欣赏美丽的红叶”可知，不是所有的树叶的颜色都来自叶绿素，故选D。