单项选择题
A.the monitoring equipment is out of order
B.separating effect becomes bad
C.inner wall is contaminated
D.separating effect becomes bad and inner wall is contaminated
单项选择题 When starting air-conditioner in the winter, we should open（）in sequence. Ⅰ.alve of warming Ⅱ.alve of humidifier Ⅲ.an
单项选择题 The air-conditioner is running in the winter and to be stopped, we should（）
单项选择题 The humidifier’s valve of air-condition should be （）, when the temperature is lower than 0℃.