单项选择题
A.a hard sand shoal marked with a light B.completely submerged at all stages of the tide C.surrounded by rocks awash at low water spring tides D.a small，low，sandy islet surrounded by shoal water
An orange and white buoy with a rectangle on it display...
单项选择题An orange and white buoy with a rectangle on it displays（）.
A.directions B.distances C.locations D.All of the above
An orange and white buoy marking an area where operatin...
单项选择题An orange and white buoy marking an area where operating restrictions are in effect will be marked with which symbol? （）
A.Open-faced diamond B.Diamond with a cross C.Circle D.Rectangle
An orange and white buoy marking a danger area will hav...
单项选择题An orange and white buoy marking a danger area will have what symbol on it?（）
A.Open-faced diamond B.Diamond with a cross C.Circle D.Square
