单项选择题
A.ventilated and tagged
B.ventilated and cooled down
C.insulated and encased
D.insulated and warmed up
单项选择题 A solenoid valve used in a refrigeration system should be installed （）.
单项选择题 When a refrigeration compressor is in the ‘off’ cycle, the thermal expansion valve will（）.
单项选择题 To add refrigerant to the high side of an air conditioning system, you should introduce the refrigerant through the （）.