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

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

單項(xiàng)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