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單項選擇題

（） provides the head or pressure to supply the domestic water where required.

A.The compressed air
B.The compressing air
C.The transfer pump
D.The head tank

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Under rotary pumps are the gear, （）, cam-and-piston and screw types.

A.reciprocating
B.diffuser
C.turbine
D.vane

單項選擇題

The water level in the gauge glass when a boiler is operating is （） when the boiler is shut down.

A.lower than
B.higher than
C.below
D.equal to