单项选择题
All fog signals shall be sounded every two minutes with the exception of a vessel（）.
A.underway or making way B.under sail or under tow C.anchored or aground D.not under command or restricted in her ability to maneuver
单项选择题 According to the Rules，when should lights be displayed?（）.
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（）.
