单项选择题
Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?（）
A.Sub-cooled liquid B.Sub-cooled vapor C.Superheated vapor D.Liquid
单项选择题 The heat removed from the refrigerant in the condenser of a refrigeration plant is the （）
单项选择题 An important consideration in selecting a lubricating oil for use in a refrigeration compressor is for the oil to （）
单项选择题 Properties of a good refrigeration oil include（）
