单项选择题
A.true north
B.magnetic north
C.the vessel's beam
D.the vessel's head
单项选择题 A position that is obtained by using two or more intersecting lines of position，taken at nearly the same time，is a(n)（）.
单项选择题 A position that is obtained by applying estimated current and wind to your vessel’s course and speed is a(n)（）.
单项选择题 A position obtained by crossing lines of position taken at different times and advanced to a common time is a(n)（）.