单项选择题
A.is 14 feet above sea level B.has a fixed green light C.is shown from a white square tower D.is synchronized with a radio beacon
A.off-center B.on the centerline C.completely flooded D.open to the sea above and below the waterline
A.air bottle for breathing B.whistle and hand held flare C.whistle，strobe light and reflective tape D.whistle，hand held flare and sea dye marker