阅读理解。 What is the sky(天空)? Where is it?

题目：

阅读理解。

    What is the sky(天空)? Where is it? How high is it? What lies above it? These questions are hard to

answer, aren’t they?

     Is the sky blue? The sky has no color. We know that there is air around the world. When planes fly,

they need air to lift their wings(翼) . Planes cannot fly very high because when they go high, the air gets

thinner. If we go up about 1,200 kilometers from the earth, we find there is no air.

     Perhaps(也许) we can answer some of our questions now. The sky is space(空间). In this space

there is only the sun, the moon and all the stars.

1.What is the sky?

A. It’s the clouds      

B. It’s space.    

C It’s air      

D It’s nothing

2. The sky ______.

A. is blue        

B. is white        

C. is black    

D. has no color

3. Planes cannot fly very high because ______.

A. the air becomes thinner                        

B. the flying machine is not good        

C. people will be afraid if the planes fly too high      

D. it is not necessary for planes to fly so high

4. If we go up about 1,200 kilometers from the earth, we find ______.

A. there is more air  

B. there is less air  

C .there is nothing but air  

D there is no air

5. In space there is ______.

A. nothing                            

B. air everywhere    

C. everything                          

D. only the sun ,the moon and all the stars