单项选择题
A buoy having red and green horizontal bands would have a light characteristic of（）.
A.group occulting B.composite group flashing C.Morse letter A D.quick flashing
单项选择题 A cabinet or space containing the controls or valves for the fixed firefighting system must be（）.
单项选择题 A carbon dioxide fire extinguisher should be recharged（）.
单项选择题 A certificated lifeboatman assigned to command the lifeboat must（）.
