单项选择题
A.turn off all lights that interfere with the navigation lights
B.turn on all available working lights on deck
C.ring the bell rapidly for five seconds once a minute
D.display two black diamonds in a vertical line during the day
单项选择题 A helmsman receives the command “Right 15 degrees rudder.”The helmsman’s IMMEDIATE reply should be（）.
单项选择题 A heavy，thick-walled tube，usually steel，used between the drill pipe and the bit in the drill stem to weight the bit in order to improve its performance is called a（）.
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（）.