晶闸管整流电路中，常用单结晶体管做触发电路（）.A．触发 B．

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问题单项选择题

晶闸管整流电路中，常用单结晶体管做触发电路（）.

A．触发

B．保护

C．指示

D．限流

答案

参考答案：A

解答题

先化简下式，再求值：5（3a²b-ab²）-4（-ab²+3a²b），其中a=-2，b=3．

单项选择题

A．(A) Because she likes the city’s mild climate that is beneficial to her health.

B．(B) Because she loves to work with young people and share her experience.

C．(C) Because she does not have the required certificate in business management.

D．(D) Because she does not think that she has earned quite enough from her previous job.