单项选择题
Vessels required to be equipped with an approved backfire flame arrester are（）.
A.those with diesel engines B.all those with gasoline engines C.those with large engines only D.None of the above
单项选择题 The ship has a diesel engine（）a supercharger.
单项选择题 The pivot pin at the base of a sheath-screw boom davit must be（）.
单项选择题 The part of a windlass which physically engages the chain during hauling or paying out is the（）.
