单项选择题
The compass heading of a vessel differs from the true heading by（）.
A.compass error B.variation C.magnetic dip D.deviation
单项选择题 The compass error of a magnetic compass that has no deviation is（）.
单项选择题 The compass deviation changes as the vessel changes（）.
单项选择题 Quadrantal error in a gyrocompass has its GREATEST effect（）.
