单项选择题
Centrifugal pumps are popular because they are very simple in construction,and produce smooth, constant, （） discharge.
A.non-pulsating B.pulsating C.positive D.non-positive
单项选择题 The emergency bilge suction or bilge （） is used to prevent flooding of the ship.
单项选择题 In （） pump a closed discharge valve will not cause excessive pressure to build up.
单项选择题 Centrifugal pumps are non-positive and a fairly （） unit.
