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问题 单项选择题

膨胀机加温时，则（）。

A.空气进出口阀应关闭，紧急切断阀应关闭，膨胀机喷咀应打开。

B.膨胀机前的过滤器也一定被加温。

C.加温气体流路方向与膨胀空气的流路方向相反。

D加温时应关闭膨胀机的密封气。

答案

参考答案：C

完形填空

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One of the many things we take for granted in the twentieth century is the speedy collection and delivery of letters to and from all parts of the world at ___小题1:____ ( astonish ) cheap rates.

A husband away __小题2:__ a business trip can write home to his wife two thousand miles away knowing that the letter will reach __小题3:___ in a few days. His special airletter may cost him less than a loaf of bread __小题4:__ his own bus fare to work.

This service, however, is a favor of comparatively recent origin. Until modern times, the cost of sending letters privately was so great that the __小题5:___ ( arrive ) of a letter was a considerable event and might even cost financial hardship to the receiver ___小题6:___ had to bear the charges.  __小题7:___ the Middle Ages on，there were indeed special messengers ___小题8:___ ( carry ) state correspondence, and other messengers employed to travel with between the great monasteries or the great merchants’ houses, but for centuries there was no official post service by which private letters could be sent. It was not until 1840 ___小题9:___ the official organization known as the Penny Post __小题10:__ ( establish ) in Great Britain and gave ordinary people cheap and efficient postal deliveries.
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多项选择题

水库发电调度的目的是（）。

A.充分利用水能

B.增加发电量

C.保证系统安全运行

D.降低下游防洪风险
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