—I've been trying to            him for twenty minutes. Why won't he stop crying?

—Ah, Can't you see he is cutting onions? [ ]

A.cheer on

B.cheer up

C.cheered on

D.cheered up

( )电力装置回路，应测量交流电压。

A．发电机
B．交流系统的各段母线
C．根据生产工艺的要求，需监测交流电压的其它电力装置回路
D．照明