单项选择题
A.information or regulatory buoy that has lateral significance
B.buoy that is off-station and is marked to warn mariners of its wrong position
C.dual purpose marking used where the ICW and other waterways coincide
D.buoy that was set in error and will be replaced with a red nun buoy
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（）.
单项选择题 A flooded leg on a liftboat would adversely affect the vessel’s stability underway by（）.
单项选择题 A fixed carbon dioxide extinguishing system for a machinery space，designed WITHOUT a stop valve in the line leading to the protected space，is actuated by（）.