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單項選擇題

（） will be used to blow away the combustion products from the tube surfaces.

A.The blow down valve
B.The scum valve
C.The air release cock
D.The soot-blower

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單項選擇題

In motor ship, （） is often used to recover some of the heat carried in the exhaust gases from the main engine.

A.an diesel oil heater
B.a waste heat boiler
C.a fresh water generator
D.all the above

單項選擇題

Impurities from the boiler water surface can be removed through the （）.

A.safety valve
B.blow down valve
C.scum valve
D.feed check valve