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單項(xiàng)選擇題

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

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

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單項(xiàng)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

單項(xiàng)選擇題

Large pipes or （） are fitted between the steam and water drums to ensure good natural circulation of water.

A.fire-tubes
B.furnaces
C.down-comers
D.soot-blowers

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