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單項選擇題

The safety valves are mounted in pairs to （） the boiler against overpressure.

A.use
B.release
C.protect
D.effect

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單項選擇題

The defective place in the furnace should be （） with fire bricks.

A.paved
B.cleaned
C.welded
D.dismantled

單項選擇題

The exhaust boilers are used to recover some of （） carried in the exhaust gas from the main engine.

A.water
B.oil
C.heat
D.steam

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