单项选择题
A.close Fan and Humidifier at the same time
B.firstly close Fan and then close humidifier immediately
C.firstly close humidifier and then close Fan immediately
D.firstly close humidifier and then close Fan after 30 seconds
单项选择题 The humidifier’s valve of air-condition should be （）, when the temperature is lower than 0℃.
单项选择题 The humidifier’s valve of air-conditioner should be （）, when the temperature is 5~8°C in the winter.
单项选择题 In the management of the shafting, because（） carry heavy load and caused high temperature easily, it should be paid attention.