电气设备运行时，允许（）。
A.停用主保护
B.停用后备保护
C.主保护投入时，短时停用后备保护
参考答案：C
—LiYang is a hard-working boy.
—I agree. But he shouldn't _______ too late at night, or he'll be stressed out. [ ]
A. look up
B. stay up
C. make up
D. wake up
Those are her ______.[ ]
A. sister
B. brother
C. friends
D. father
