单项选择题
A.rapidly
B.by gravity
C.through a standard orifice at a specified temperature
D.at a rate of 60cc per second
单项选择题 When liquid reaches the compressor of a refrigeration system through the suction line, the condition is called （）.
单项选择题 What is a function of the wearing rings used in most centrifugal pumps?（）
单项选择题 If air at 95℃ dry bulb temperature and 50% relative humidity is conditioned to 75℃ dry bulb temperature and 50% relative humidity, it is an example of （）.