常用的低压开关有闸刀开关、()、磁力启动器、自动空气开关。
参考答案:交直流接触器
_____ is known to all, the age _______ children can go to school is seven.
A.What; which
B.It; when
C.As; at which
D.Which; when
在紧急情况下,()用有绝缘杆的钢丝钳断开带电的绝缘照明线。
A.禁止
B.允许
C.严禁
D.不能够