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问题 单项选择题

一台他励直流电动机额定数据为：PN=2.2kW，UN=220V，nN=1500r/min，ηN=0.81，电枢回路电阻Ra=1.813Ω。电机以1200r/min的稳定转速吊起重物。若采用能耗制动方法停车，并要求起始制动电流为2IN时，电枢电路中应串入的电阻为( )Ω。

A．(A) 6.398

B．(B) 4.585

C．(C) 6.089

D．(D) 7.902

答案

参考答案：B

完形填空

In order to know a foreign language thoroughly(彻底地), four things are necessary. Firstly, we must understand the language when we hear  ______小题1:________ spoken.. Secondly, we must be able to speak it correctly with confidence(自信) and without hesitation(犹豫). _____小题2:_______ , we must be able to read the language , and fourthly, we must be able to write it. We must be able to make sentences that are grammatically correct.

There is no easy way to success _____小题3:_______ language learning. _____小题4:________ good memory is of great help, but it is not enough only _____小题5:________(memorize) rules from a grammar book. It is not much use learning by heart long list of words and ______小题6:_________meaning, studying the dictionary and so on. We must learn by using the language. _______小题7:_______we are satisfied with only a few rules we have memorized, we are not really learning the language. “Learn through use” is a good piece of _____小题8:______(advise) for those ______小题9:______are studying a new language. Practice is important. We must practise speaking and ____小题10:____(write) the language whenever we can.
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单项选择题

凡不符合原计划产品标准，但符合其它产品标准的钢材为（）。

A．合格品

B．让步产品

C．不合格品

D．改判品
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