单项选择题
The quadrantal spheres are used to（）.
A.remove deviation on the intercardinal headings B.remove deviation on the cardinal compass headings C.remove heeling error D.compensate for induced magnetism in vertical soft iron
单项选择题 The principal purpose of magnetic compass adjustment is to（）.
单项选择题 The permanent magnetism of a vessel may change in strength due to（）.
单项选择题 The permanent magnetism of a vessel may change in polarity due to（）.
