单项选择题
A.suction side of a bilge pump
B.exhaust manifold of an auxiliary diesel
C.discharge line from an air compressor
D.chemical feed tank of an evaporator
单项选择题 Which of the listed statements is correct concerning the starting of centrifugal pumps?（）
单项选择题 Excessive oil foaming in the crankcase of a refrigeration compressor at start up can cause（）.
单项选择题 Which of the valves listed is NOT considered to be a hydraulic system directional control valve?（）