单项选择题
The Flinders bar on a magnetic compass compensates for the（）.
A.induced magnetism in vertical soft iron B.induced magnetism in horizontal soft iron C.permanent magnetism in ship's steel D.vessel's inclination from the vertical
单项选择题 The error in a magnetic compass caused by the vessel’s magnetism is called（）.
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（）.
