97免费在线观看视频,亚洲综合自拍网,黄色毛片免费观看,热久久综合网,免费看日产一区二区三区 狠狠操av,久久久涩涩涩,在线精品免费视频,人人插天天干,久久91精品国产91久久

單項(xiàng)選擇題

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

微信掃碼免費(fèi)搜題