The students _____ at home on Sundays.[ ]
A. stay
B. stays
C. staies
D. to stay
答案:A
采集飘尘的采样高度是
A.0.5m B.1.0m C.1.5m D.3~5m E.5~15m
电空控制器手柄从“过充”位回“运转”位后,过充压力需要自然消除的时间约为()。
A.100S
B.120S
C.140S