1. When autumn comes, the _______(树叶) on the trees begin to turn yellow.
2. It's _______(不可能的) that he can come here before noon.
3. The singing sounds quite _______(美妙), doesn't it?
4. The students had their photos _______(拍照) in the middle of the square.
5. To be a doctor for children is very _______(值得的).
6. The children _______(认为) their teacher as a good friend.
7. Who _______(赢)the boys' long jump?
8. Which team _______(打败) the team from No.2 Middle School?
9. The bike is too expensive. I don't think it's worth _______(买).
10. My child _______(更喜欢) drawing to singing.

         Leaves are nature's food factories. Plants take water from the ground through their roots. They take a gas
called carbon dioxide (CO₂) from the air. Plants use sunlight to turn water and CO₂ into glucose. Glucose is a
kind of sugar. Plants are glucose as food for energy to grow. The way plants turn water and CO₂ into glucose
is called photosynthesis. That means "putting together with light". A chemical called chlorophyll helps make
photosynthesis happen. Chlorophyll is green. It gives plants their green colour.
         As summer ends and autumn comes, the days get shorter and shorter. This is how the trees "know" to
begin getting ready for winter.
         During winter, there is now enough light or water for photosynthesis. The trees will rest, and live on the
food they have stored during the summer. They begin to close their food-making factories. The green
chlorophyll disappears from the leaves. Then, we begin to see yellow and orange colours. A few of these colors
stay in the leaves all the time. We just can't see them in the summer, because they are covered up by the green
chlorophyll.        
          Red and purple colors we see in leaves are made mostly in the autumn. In some trees, like maples (枫树),
glucose is stored in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this
glucose into red. The brown color of trees like oaks (橡树) is made from wastes left in the leaves.

1. The word "chlorophyll" in the first paragraph means ____ in Chinese.

A. 叶绿素
B. 氧气
C. 胡萝卜素
D. 蛋白质

2. Where is carbon dioxide from?

A. Ground.
B. Roots.
C. Sunlight.
D. Air.

3. The way ______ is called photosynthesis.

A. plants get carbon dioxide from the air
B. plants take water from the ground
C. plants turn water and carbon dioxide into glucose
D. plants use glucose as food for energy to grow

4. Red and purple colors in leaves are made mostly in ______.

A. spring
B. autumn
C. summer
D. winter

5. ______ in the leaves changes into red color in autumn.

A. Sunlight
B. Water
C. Glucose
D. Chlorophyll