单项选择题
Some ships have（）(特殊职责) ,such as tugs.
A. duty B. special duties C. special duty D. special
单项选择题 （）（货船）can be divided into two basic types.
单项选择题 The most modern ship is（）（集装箱船）.
单项选择题 A few ships carry（）（旅客）.
