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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

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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

單項(xiàng)選擇題

（） system is arranged to ensure that water can be drawn from any tank or the sea and discharged to any other tank or the sea as required to trim the vessel.

A.The domestic water
B.Bilge water
C.Oil transfer
D.The ballast