单项选择题
A.three masthead lights in a vertical line instead of either the forward or after masthead light
B.two masthead lights in a vertical line instead of either the forward or after masthead lights
C.two towing lights in a vertical line at the stern
D.a small white light aft of the funnel
单项选择题 A power-driven vessel shall have her engine ready for（）when the visibility is restricted.
单项选择题 A power-driven vessel not under command at night must show her sidelights when（）.
单项选择题 A power-driven fishing vessel is underway on the high seas and is not engaged in fishing. Which of the following factors determines what lights she will show?（）.