单项选择题
The device used for low-pressure control and high-pressure cutout on a compressor is called a（）
A.cutout B.pressure controller C.controller switch D.cutout switch
单项选择题 The purpose of the purge valve at the top of the condenser in a refrigerating system is to（）
单项选择题 What is the purpose of sub cooling R-12 in the condenser?（）
单项选择题 In terms of pressure and temperature in the refrigerant in the compressor, what happens to the primary?（）
