单项选择题
A relative bearing is always measured from（）.
A.true north B.magnetic north C.the vessel's beam D.the vessel's head
单项选择题 A preferred-channel buoy will show a（）.
单项选择题 A preferred-channel buoy may be（）.
单项选择题 A plane that cuts the Earth’s surface at any angle and passes through the center will always form（）.
