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單項選擇題

A （） pump is that where the volume of the pump chamber is alternately increased to draw the liquid in and then decreased to force the liquid out.

A.injector
B.positive displacement
C.centrifugal
D.centripetal

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單項選擇題

A reciprocating pump belongs to （） according to its working principle.

A.injector pumps
B.positive displacement pumps
C.centrifugal pump
D.centripetal pumps

單項選擇題

Shaft sealing in a centrifugal pump can be effected by （）.

A.the mechanical seal
B.packed stuffing boxes
C.either A or B
D.neither A nor B