单项选择题
A.During the hours of darkness
B.At all times when underway
C.From sunset to sunrise and restricted visibility
D.Sunrise to sunset
单项选择题 A vessel towing where the tow prevents her from changing course shall carry（）.
单项选择题 A vessel towing is showing three forward white masthead lights in a vertical line. This means that the length of the（）.
单项选择题 A vessel is fishing at anchor on the high seas. Which of the following day signals should she display if she has gear extending out over 150 meters horizontally from the vessel?（）.