单项选择题
Quadrantal error in a gyrocompass has its GREATEST effect（）.
A.in high latitudes B.near the equator C.on north or south headings D.on intercardinal headings
单项选择题 Magnets are placed in horizontal trays in the compass binnacle to compensate for the（）.
单项选择题 Magnetic variation changes with a change in（）.
单项选择题 Magnetic heading differs from compass heading by（）.
