单项选择题
A.Loaded displacement minus light displacement
B.Gross tonnage minus net tonnage
C.Loaded displacement minus net tonnage
D.Light displacement minus the weight of the vessel
单项选择题 A well in the uppermost deck of a shelter deck vessel which has only a temporary means of closing for the purpose of gaining an exemption from tonnage measurement is called a（n）（）.
单项选择题 A tackle by which the outer end of a boom is raised and lowered is the topping（）.
单项选择题 A stopper is（）.