单项选择题
A triangular daymark would be colored（）.
A.red B.red and white C.green D.green and white
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?（）
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)（）
