三相笼型异步电动机电源反接制动时需要在（）中串入限流电阻。
A、控制回路
B、定子回路
C、转子回路
D、直流回路
参考答案：B
Do you think that people are _______off than they were five years ago as our standard of living is improving.
A．well
B．worse
C．better
D．badly
实验室检测立克次体时下列哪种是最常用的分离标本( )
A．尿B．粪便C．血液D．头发E．痰
