交流调功器利用晶闸管的___________实现交流功率的调节。
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a lot of rain in out hometown in summer.
A. There is
B. There has
C. We have
D. We has
There is going to a class meeting this afternoon.
A. have
B. hold
C. is
D. be
There a lot of traffic at this time of day. so you'd better careful.
A. has, be
B. have,been
C. is, be
D. are, be
there enough good news in today's newspaper?
A. Is
B. Are
C. Was
D. Were