单项选择题
A heavy steel curved arch constructed athwartships and above the after deck on a towing vessel is sometimes called a（）.
A.main brace B.tow span C.jockey bar D.None of the above
单项选择题 A head-on situation at night is one in which you see dead ahead a vessel showing（）.
单项选择题 A hand held instrument used to measure distances between objects and the ship is a（）.
单项选择题 A green buoy has a yellow triangle on it. This is a(n)（）.
