单项选择题
A.one sidelight
B.one sidelight and a masthead light
C.one sidelight and two masthead lights
D.both sidelights of a vessel and her masthead light(s)
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)（）.
单项选择题 A frame with two，or sometimes four，arms through which are threaded the guidelines and which is used to keep the drill stem and bit in line with the center opening in the temporary guide base is the（）.