单项选择题
A.the ability of oil to separate from water
B.the temperature at which oil flows rapidly
C.a measure of the water in a lube oil system
D.an emulsion of different grades of oil
单项选择题 When subjected to high heat from a open flame, or an electric heating element, which of the listed refrigerants will break down and produce phosgene gas?（）
单项选择题 Which of the following terms is used to identify the pressure of the liquid entering a pump?（）
单项选择题 Ammonia when used as a refrigerant is valuable because of its high efficiency, it is however （）.