The rocket engine, with its steady roar like that of a waterfall or a thunde

游客2024-01-18 44

问题 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【C1】______powerful enough to shoot astronauts【C2】______the earth’s gravitational pull and【C3】______them on the moon. We have now become【C4】______in space.
Impressive and complex【C5】______it may appear, the rocket, which was【C6】______in China over 800 years【C7】______, is a relatively simple device. Fuel that is【C8】______in the rocket engine changes【C9】______gas. The hot and rapidly【C10】______gas must escape, but it can do so only through an opening that faces backward. As the gas is radiated with great force, it pushes the rocket in the opposite direction. [br] 【C7】

选项 A、in advance
B、before
C、earlier
D、ago

答案 D

解析 ago“在……以前”。该句为which引导的定语从句，意为“中国发明火箭是在距今800多年前”。句中谓语是一般过去时，故应选D。

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