单项选择题
The error in a magnetic compass caused by the vessel’s magnetism is called（）.
A.variation B.deviation C.compass error D.bearing error
单项选择题 The directive force of a gyrocompass（）.
单项选择题 The difference between magnetic heading and compass heading is called（）.
单项选择题 The compass heading of a vessel differs from the true heading by（）.
