答案:B
_____ the catastrophe happened that the local government realized the importance of substantial development.
A.It was until
B.Not until
C.Until
D.It was not until
2.2kW的异步电动机,运行于相电压为220V的三相电路,已知电动机效率为81%,功率因数0.82,这台电动机的额定电流为()。
A.4A
B.5A
C.8.7A
D.15A