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问题 选择题

当今世界，国际局势发生了深刻的变化，经济全球化、科技进步日新月异、综合国力竞争日趋激烈。因此，在对外开放中[ ]

A．既要积极敞开国门，又要维护自身安全

B．要全面吸引

C．要吸收和借鉴国外的一切东西

D．只对世界上的发达国家开放

答案

答案：A

填空题

小聪在将暖水瓶中的水灌好后，随手盖上瓶塞．过了一会儿，突然听到“嘭”的一声，暖水瓶内的水蒸气将瓶塞冲起，同时看到瓶口冒出“白气”．在这个过程中的能量转化过程与汽油机的______冲程能量转化过程相同．
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单项选择题

The great advance (91) rocket theory 40 years ago showed that liquid-fuel rockets were far (92) in every respect to the skyrocket with its weak solid fuel, the only kind of rocket then known. (93) , during the last decade, large solid-fuel rockets with (94) fuels about as powerful as liquid fuels have (95) their appearance, and it is a favorite layperson’s question to (96) which one is "better". The question is meaningless. (97) might as well ask whether a gasoline or a diesel engine is "better". It all (98) on the purpose. A liquid-fuel rocket is complicated, (99) has the advantage that it can be controlled beautifully. The burning of the rocket engine can be stopped completely; it can be reignited when (100) . (101) , the thrust can be made to vary by adjusting the speed of the fuel pumps. A solid-fuel rocket, on the other hand, is rather (102) in construction, (103) hard to build when a really (104) size is desired. But once you have a solid-fuel rocket, it is ready for action (105) very short notice. A liquid-fuel rocket has to be fueled first and cannot be (106) readiness for very long after it has been fueled. (107) , once a solid-fuel rocket has been ignited, it will keep burning. It cannot be stopped and reignited (108) desired (it could conceivably be stopped and reignited after a pre-calculated time of burning has elapsed, and its thrust cannot be varied. Because a solid-fuel rocket can be kept ready for a long time, most military missiles (109) solid fuels, but human-piloted spaceflight needs the fine adjustments that can (110) be provided by liquid fuels.

A．expend

B．employ

C．consume

D．utilize
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