单项选择题 Deadweight，which is the cargo carrying capacity of a vessel in tons，is determined by（）.

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（）.