单项选择题
A SEAMARK，I.E. A BUOY，INDICATING THE NORTH，EAST，SOUTH OR WEST FROM A FIXED POINT，E.G. A WRECK is（）.
A.Entrance buoy B.New buoy C.Port buoy D.Cardinal buoy
单项选择题 A rock and sand structure extending from the bank of the river toward the channel is known as a（）.
单项选择题 A relative bearing is always measured from（）.
单项选择题 A preferred-channel buoy will show a（）.
