单项选择题
A.a red light over a white light B.a white light over a red light C.a green light over a white light D.two red lights in a vertical line
A.a vessel restricted in her ability to maneuver B.a vessel not under command C.a vessel constrained by her draught D.a vessel not under way
A.under sail B.restricted in her ability to maneuver C.crossing a channel D.All of the above