单项选择题
The emergency bilge suction or bilge （） is used to prevent flooding of the ship.
A.injection valve B.relief valve C.discharge valve D.inlet filter
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.
单项选择题 Gear pumps are （） type because they discharge a near constant amount of liquid regardless of pressure.
