用来控制液压油路的走向，使油缸活塞杆伸出或收回的是（）。
A.压力表
B.液位液温计
C.电磁换向阀
D.齿轮泵
参考答案：C
氯己定液口腔内及创口消毒浓度为
A．0.1%
B．0.2%
C．0.3%
D．0.5%
E．1.0%
Does it ever ______ to you that they would be punished for being late?
A．strike
B．occur
C．happen
D．appear
