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單項選擇題

In a （） the center screw is driven and the outer screws idle.

A.single screw pump
B.double-screw pump
C.triple screw pump
D.centripetal pump

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單項選擇題

The discharge flow of a reciprocating pump is （）.

A.steady
B.in pulsation
C.continuous
D.large

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A centrifugal pump produces the required pressure energy by means of a rotating （） provided with vanes.

A.propeller
B.impeller
C.circumference
D.screw