单项选择题
Centrifugal pumps are non-positive and a fairly （） unit.
A.low pressure B.low discharge C.low speed D.high pressure
单项选择题 Gear pumps are （） type because they discharge a near constant amount of liquid regardless of pressure.
单项选择题 （） are more suitable for large quantities at low pressure.
单项选择题 The various pumps and lines are （） to some extent so that each pump can act as an alternative for another.
