单选题
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 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 384000 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 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.

单选题 Scientists have known ______ the moon is.

A. how long
B. how big
C. how old

【正确答案】 B

【答案解析】[解析] 细节题。根据第三句可知：科学家已经知道月亮有多大，距离地球有多远。故B为正确答案。

单选题 The earth is about 384000 kilometers away from the ______.

A. space
B. universe
C. earth

【正确答案】 C

【答案解析】[解析] 细节题。第一段第六句指出：月亮距离地球384000千米。故C为正确答案。

单选题 A plane cannot fly to the moon because ______.

A. there is no air above 240 kilometers away from the earth
B. there is no gas in the plan
C. the plane is not strong enough

【正确答案】 A

【答案解析】[解析] 细节题。根据第一段倒数第三句可知：飞机不能飞到月球的原因是：地球外240千米就没有空气了。故A为正确答案。

单选题 The hot gas in the rocket is used for ______.

A. keeping the air in the rocket fresh (新鲜的)
B. keeping the men in the rocket warm
C. making the rocket fly up

【正确答案】 C

【答案解析】[解析] 细节题。第二段第三句指出：热气会让火箭飞向天空。故C为正确答案。

单选题 Several rockets without men in them have flown to ______.

A. the stars
B. another satellite of the sun
C. the sun

【正确答案】 B

【答案解析】[解析] 细节题。第二段倒数第二句指出：数架无人火箭已经飞向其他行星。故B为正确答案。