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單項(xiàng)選擇題

The propeller consists of a （）with several blades of helicoidal form attached to it.

A.shaft
B.boss
C.wheel
D.lever

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單項(xiàng)選擇題

Oil pressure in the lubrication system is（）than the static sea water head to ensure that sea water cannot enter the sterntube in the event of seal failure.

A.higher
B.lower
C.very higher
D.very lower

單項(xiàng)選擇題

（）is used to prevent the entry of sea water to the machinery space.

A.A special sealing gland
B.Propeller
C.Tailshaft
D.Sterntube bearing

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