单项选择题
A.rate of doing work
B.amount of force needed to overcome friction
C.amount of work accomplished
D.distance through which an object is moved
单项选择题 To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to （）.
单项选择题 On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.
单项选择题 While troubleshooting a refrigeration system for low head pressure, liquid refrigerant flooding back from the evaporator is determined to be the causeIt may be necessary to （）.