当某一电气元件的主保护或断路器拒绝动作时,能够以较长的时间切除故障的保护叫()
A、后备保护
B、辅助保护
C、越级保护
D、差动保护
参考答案:A
朱砂入药的正确炮制方法是()
A.水飞
B.炙
C.煅
D.煨
E.淬
-Hello, mum. Are you still on Lushan Mountain?
-Oh, no. We are back home. We _________ a really good journey.
A.have
B.had
C.are having
D.will have