单项选择题
A ruptured diaphragm in a thermostatic expansion valve will cause the valve to （）.
A.open B.close C.remain in its position D.flood the evaporator with refrigerant
单项选择题 Black smoke coming from a boiler can be caused by （）.
单项选择题 Which will cause the high pressure cutout to stop the compressor in a R-22 system?（）
单项选择题 Insufficient refrigerant in a refrigeration plant may result in （）.
