单项选择题
A.easterly courses in high latitudes
B.southerly courses in high latitudes
C.westerly courses in low latitudes
D.easterly courses in low latitudes that cross the equator
单项选择题 A gnomonic projection is based on a(n)（）.
单项选择题 （）refers to the angle between true North and the heading line of the ship.
单项选择题 （）is the distance east or west measured in degrees，minutes and seconds of arc on the equator between the prime meridian and the meridian passing through the place.