单项选择题
The （）pump is usually used as the emergency bilge pump.
A.turbine B.screw C.vane D.ejector
单项选择题 When starting a reciprocating pump, the inlet valve should be （）.
单项选择题 When starting a centrifugal pump, the discharge valve should be （）.
单项选择题 When start a screw pump, the by pass valve should be （）.
