异步电动机工作时,电源电压变化对电动机的正常工作()
A.有一定影响
B.影响很小
C.没有影响
参考答案:A
-5的倒数为______,-5的相反数为______.
We have happiness, _________ still we have trouble sometimes. That's life. [ ]
A. so
B. because
C. but
D. and