单项选择题
A vessel towing a barge astern would show，at the stern（）.
A.only a stern light B.a towing light above the stern light C.two towing lights in a vertical line D.two white lights in a vertical line
单项选择题 A vessel sighting a northern right whale dead ahead should（）.
单项选择题 A vessel showing a rigid replica of the International Code flag “A” is engaged in（）.
单项选择题 A vessel showing a green light over a white light in a vertical line above the level of the sidelights is（）.
