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?（）
A.One B.Two C.Three D.Four
单项选择题 A towing light，according to the Rules，is a（）.
单项选择题 A towing light is a yellow light having the same characteristics as a(n)（）
单项选择题 A single towing light will be carried above a vessel’s sternlight（）.
