单项选择题
A vessel being towed astern，where the length of the tow exceeds 200 meters，will exhibit （）.
A.two balls in a vertical line B.a diamond shape where it can best be seen C.a ball on each end of the tow D.no dayshape
单项选择题 A tug is towing three manned barges in line in fog. The first vessel of the tow should sound （）.
单项选择题 A triangular daymark would be colored（）.
单项选择题 A towing vessel 30 meters in length is pushing barges ahead. How many white masthead lights is the vessel REQUIRED to show at night?（）
