单项选择题
A “sheepshank” is used to（）.
A.keep a line from fraying B.join lines of unequal size C.stop off a line D.shorten a line
单项选择题 （）provide athwartship support for the mast or king posts.
单项选择题 （）are used for anchor gear in marine work where the chains must withstand the corrosive effects of seawater.
单项选择题 （） are two vertical supports，usually steel，one each side of the centerline of the ship used to support booms.
