单项选择题
The relief valve is located on the（）
A.discharge side of condenser B.discharge side of compressor C.outlet of the evaporator D.receiver tank
单项选择题 If the compressor-discharge temperature is higher than the receiver temperature（）
单项选择题 If the head pressure is too high,（）
单项选择题 If no gaskets are used in the piping joints of a Freon system, the joints must be（）
