单项选择题
A mixed-flow pump is a （） pump classified by the working principle.
A.self priming B.positive displacement C.reciprocating D.impeller
单项选择题 The （）pump is usually used as the bilge feed pump to an oily water separator.
单项选择题 The （）pump is usually used as the emergency bilge pump.
单项选择题 When starting a reciprocating pump, the inlet valve should be （）.
