阅读理解。
Scientists have always wanted to know more about the universe.
Years ago they knew many things about the moon. They knew how big it was and how far away it was from the earth. But they wanted to know more about it. They thought the best way was to send men to the moon.
The moon is about 384 000 kilometers away from the earth. A plane cannot fly to the moon because the air reaches only 240 kilometers away from the earth. But something can fly even when there is no air. That is a rocket(火箭)
How does a rocket fly? There is gas(气体)in the rocket. When the gas is made very hot inside the rocket, it will rush out of the end of the rocket, so it can make the rocket fly up into the sky.
Rockets can fly far out into space. Rockets with men in them have been to the moon. Several rockets without men in them have flown to another planet(行星)much farther away than the moon. One day rockets may be able to go to any place in space.
1. Scientists have known _____ the moon is.
A. how long
B. how heavy
C. how old
D. how big
2. The earth is about 384 000 kilometers away from the _____.
A. space
B. universe
C. sun
D. moon
3. A plane cannot fly to the moon because _____.
A. there is no air 240 kilometers above from the earth
B. there is no gas in the plane
C. the plane is not strong enough
D. the plane must be driven by a man
4. The hot gas in the rocket is used for _____.
A. keeping the air in the rocket fresh(清新的)
B. keeping the men in the rocket warm
C. making the rocket fly up
D. cooking food for the men
5. Several rockets without men in them have flown to _____.
A. the stars
B. the satellites of the sun
C. the sun
D. another planet of the sun

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