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單項(xiàng)選擇題

（） supplies pilot air to control the cylinder air start valves.

A.An air compressor
B.An indicator cock
C.An air distributor
D.A safety valve

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單項(xiàng)選擇題

（） may have two emergency source of power, thus requiring two emergency switchboards.

A.Large passenger vessels
B.General cargo ships
C.Container ships
D.Oil tankers

單項(xiàng)選擇題

（） usually helps to induce air movement to assist combustion.

A.Cylinder cover
B.Main bearing
C.The exhaust valve
D.The piston movement