单项选择题 In determining safe speed，all of the following must be taken into account EXCEPT the（）.

单项选择题 When a vessel sees the other ahead or nearly ahead，by night she could see the masthead lights of the other in a line or nearly in a line or both side lights，（）shall be deemed to exist.

单项选择题 When in sight of another vessel，any action taken to avoid collision must（）.