单项选择题
If the temperature in the icebox is too high, the trouble could be（）
A.a clogged scale trap B.air in the system C.automatic controls not functioning properly D.insufficient cooling water to the condenser
单项选择题 Air or noncondensable gas is removed from a refrigeration system by a （）
单项选择题 Where are the zinc plates located?（）
单项选择题 The device used for low-pressure control and high-pressure cutout on a compressor is called a（）
