单项选择题
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
单项选择题 （）is used to prevent the entry of sea water to the machinery space.
单项选择题 The thrust from the propeller to the hull of the ship is transferred by（）
单项选择题 The transmission system transmitting power from the engine to the propeller is composed of shafts, bearings, and（）
