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全部科目 > 水路交通运输技能考试 > 海船船员考试 > 船舶管理(驾驶专业) > 航海英语 > 船舶及其结构 > 船舶动力装置

单项选择题

The pivot pin at the base of a sheath-screw boom davit must be().

A.inserted each time before the booms are cranked out
B.periodically removed for inspection and lubricated
C.replaced at each inspection for certification
D.in the locked position after the boat is cradled and griped down

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