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【单选题】
关于X线机所用继电器或接触器的叙述,哪组是错误的?( )A.
极化继电器的衔铁在不工作时，永远停留在中间位置；
B.
交流接触器工作时，铁心可产生涡流和磁带损耗，直流接触器没有此现象；
C.
延时继电器的特点，是接点在闭合或断开时，有一定的延迟时间；
D.
直流接触器铁心可由整块钢材制成；
E.
交流接触器铁心应装有分磁环
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【单选题】Different ______ different ______.
A.
countries have；weather
B.
country have；weathers
C.
countries have；weathers
D.
country has；weather
【单选题】From the passage we can conclude that______.
A.
different people have different ideas about the same thing
B.
Westerners culture is similar to our Chinese culture
C.
in general, Westerners and the Chinese don't like pigs
D.
all of the Chinese like pigs better than Westerners
【简答题】阅读理解。 Different countries and different people have different manners (礼貌). We must know their customs (风俗习惯), or they will think we are ill-mannered (不礼貌). If you visit a Chinese family, you should k...
【单选题】锅炉水冷壁管内结垢后可造成( )A．传热增强，管壁温度升高B．传热减弱，管壁温度降低C．传热增强，管壁
A.
锅炉水冷壁管内结垢后可造成( ) A.传热增强，管壁温度升高
B.
传热减弱，管壁温度降低
C.
传热增强，管壁温度降低
D.
传热减弱，管壁温度升高
【简答题】We have known for a long time that flowers of different plants open and close at different times of day. This is so 1 that there seems to be no need to ask the reason for it. Yet no one 2 understands ...
【单选题】Different nations have different cultures,so we should get a thorough understanding about the cuhural ________. [ ]
A.
obesity
B.
various
C.
consequence
D.
diversity
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