How can a rocket fly?

Rockets can fly far out into space. Rockets made by the USA and Russia with man inside them have already reached the moon. Several rockets without man have been sent to other worlds much farther away. On Nov. 7, 2007, China’s first lunar probe (月球探测器), Chang’e I, successfully  completed its 1,580,000km flying journey to the moon.

I am sure that you are asking: How does a rocket fly? If you want to know, get a balloon and then blow it up, until it is quite big. Do not tie up the neck of the balloon, let it go. The balloon will fly off through the air very quickly. The air inside the balloon tries to get out. It rushes out through the neck of the balloon and this pushes the balloon through the air.

This is how a rocket works. Of course, the rocket is made of metal. The metal must not be heavy but it must be very strong. There is gas inside the rocket, which is made very hot. When it rushes out of the rocket, the rocket is pushed up into the air. The jet velocity (喷射速度) is always faster than the flying speed.

We’re sure that one day rockets with man may be able to go anywhere in space.

Choose the best answer according to the passage.

1. The underlined word “balloon” in the passage means ________.

A. 气体      B. 气球      C. 气旋    D. 空气

2. The rocket is made of ________.

A. light and strong metal      

B. heavy and strong metal

C. light and strong gas        

D. heavy and strong gas

3. The underlined word “it” in the third paragraph refers to ________.

A. the rocket             B. the metal    

C. the air                  D. the hot gas

4. Which of the following is NOT right?

A. Men have been to the moon by rocket.

B. A balloon can fly if the air in it goes out completely.

C. It’s about 1,580,000km from the moon to the earth.

D. The hot gas inside the rocket can make it fly.

【答案】（反白可见）：BADB