The rocket engine, with its steady roar like that of a waterfall or a thunderstorm, is an impressive symbol of the new space age

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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【C11】______an opening that【C12】______backward. As the gas is【C13】______with great force, it【C14】______the rocket in the【C15】______direction. Like the kick of a gun【C16】______it is fired, it【C17】______the laws of nature【C18】______by Sir Isaac Newton when he discovered that"【C19】______every action, there is【C20】______equal and opposite reaction. "
【C16】

选项 A、that
B、when
C、if
D、although

答案B

解析 when引导的定语从句。
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本试题收录于: 英语题库普高专升本分类
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