直流电动机能耗制动是利用()配合实现的。
A、直流电源
B、电阻
C、交流电源
D、晶闸管
参考答案:B
This toy bear _______ be Jane's. She's the only kid at the picnic. [ ]
A. must
B. can
C. need
D. have to
It is not impossible _the important work on time. [ ]
A. for he to finish
B. for him to finish
C. that him finish
D. he to finish