39. The word “backfire” in the last paragraph most probably means “_____________”。
A) strengthen the relationship
B) start a fire in the backyard
C)produce an undesired result
D) improve management skills
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40. The passage is mainly about the importance of______________
A) management training courses for employers
B) proper relationship between managers and staff
C) setting business goals for both managers and staff
D) being a part of social networking for a good manager
关于继电器的主要功能,说法错误的是( )
A. 以小电流控制大电流;
B. 遇大电流时熔断以保护电路;
C. 减少手动开关的数量;
D. 保护较小的开关以及较细的导线。
起动机中共有( )个电刷,其中( )个位绝缘电刷。
A. 4,2
B. 2,4
C. 2,1
发电机能力转化的方式为( )。
A. 电能转化为机械能
B. 化学能转化为电能
C. 机械能转化为电能