Buoys which mark isolated dangers are painted with alternating（）.

单项选择题Buoys which mark dredging areas are painted（）.

A.black
B.yellow
C.green
D.red

单项选择题Buoys are marked with reflective material to assist in their detection by searchlight. Which statement is TRUE? （）

A.A safe-water buoy will display red and white vertical stripes of reflective material
B.All reflective material is white because it is the most visible at night
C.A special-purpose mark will display either red or green reflective material to agree with its shape
D.A preferred-channel buoy displays either red or green reflective material to agree with the top band of color

单项选择题Branford reef is（）.

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

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

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