单选题 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 (61) powerful enough to shoot astronauts (62) the earth's gravitational pull and land them on the moon. We have now become space (63) .
Impressive and complex as it may appear, the rocket, which was (64) in China over 800 years ago, is a relatively simple device. Fuel that is (65) in the rocket engine changes (66) gas. The hot and rapidly (67) gas must escape, but it can do so only through an opening that (68) backward. As the gas is (69) with great force, it (70) the rocket in the (71) direction. Like the kick of a gun (72) it is fired, it (73) the laws of nature (74) by Sir Isaac Newton when he discovered that" (75) every action, there is an equal and opposite reaction./

【正确答案】 D
【答案解析】因其后接形容词powerful作表语故应填系词。shown不是系词；been和appeared虽可作系词但与句意不符；而proved可作系词，符合句意。
【正确答案】 C
【答案解析】根据意思判断，beyond“超出，超过”。
【正确答案】 A
【答案解析】根据意思判断，travelers正确。
【正确答案】 D
【答案解析】根据词的意思区分，invented(指发明)合乎题意。
【正确答案】 D
【答案解析】根据句子意思判断，burned正确。
【正确答案】 B
【答案解析】change into是固定短语，“变成”的意思。
【正确答案】 C
【答案解析】根据句子意思判断，应选expanding gas膨胀的气体。
【正确答案】 C
【答案解析】faces"朝着”。
【正确答案】 D
【答案解析】transmit“传递”，disperse“驱散”，erect“直立，挺直”，radiate“辐射，向各方向伸展”，只有D最合题意。
【正确答案】 D
【答案解析】根据句子意思判断，应为push“推”。
【正确答案】 C
【答案解析】朝相反的方向，故选C。
【正确答案】 B
【答案解析】when引导的定语从句。
【正确答案】 C
【答案解析】根据句子意思判断，follow在这里是“遵循”的意思。
【正确答案】 A
【答案解析】根据句子意思判断，describe是“记载，描述”的意思。
【正确答案】 D
【答案解析】for是“对于”的意思。