The rocket engine, with its steady roar like that of a waterfall or a thunderstorm, is an impressive symbol of the new space age. Rocket engines have __1_ powerful enough to shoot astronauts beyond the earth´s gravitational pull and __2 __them on the moon. We have now become travelers space.

Impressive and complex __3__ it may appear, the rocket, which was invented in China over 800 years __4__ , is a relatively simple device. Fuel that is __5__ in the rocket engine changes into gas. The hot and rapidly __6__ gas must escape, but it can do so only through an opening that __7__ backward. As the gas is radiated with great force, it __8__ the rocket in the opposite direction. Like the kick of a gun that it is fired, it __9__ the laws of nature described by Sir Isaac Newton when he discovered that “for every action, there is __10__ equal and opposite reaction.”

1. A. shown B. been C. appeared D. proved

2. A. send B. land C. take D. carry

3. A. that B. so C. as D. sometimes

4. A. in advance B .before C. earlier D. ago

5. A. round B. contained C. stored D. burned

6. A. heating B. escaping C. expanding D. conducting

7. A. turns B. goes C. faces D. directs

8. A. attracts B. leads C. pulls D. pushes

9. A. states B. proves C. follows D. breaks

10. A. no B. an C .another D. the

参考答案:1.D2.B3.C4.D5.D6.C7.C8.D9.C10.B