定子绕组中性点不接地的发电机,当发电机出口侧A相接地时,发电机中性点的电压为()
A、1/3相电压
B、相电压
C、√3倍相电压
D、3倍相电压
参考答案:B
So far this year we _____ a fall in house prices by between 5 and 10 percent.
[ ]
A. saw
B. see
C. had seen
D. have seen
连续驾驶机动车几小时需要停车休息?()
A.2
B.4
C.6
D.8