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
单项选择题 The part of a windlass which physically engages the chain during hauling or paying out is the（）.
单项选择题 The most serious effect of air trapped in a diesel engine jacket water cooling system is that it（）.
单项选择题 The engine in a covered lifeboat is fueled with（）.
