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）（）.
A.Exemption space B.Tonnage deck C.Cofferdam D.Tonnage opening
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（）.
单项选择题 A stay is（）.
