单项选择题
A.manila B.nylon C.polypropylene D.dacron
A.increases the strength of the hook B.prevents the sling ring from coming out of the hook if the strain is abruptly eased C.prevents the sling ring from coming out of the hook if there is a strain on the sling ring D.All of the above
A.square knot B.carrick bend C.sheet bend D.bowline