单项选择题
A.Worn gears in the compass housing B.Magnetism from the earth's magnetic field C.Magnetism within the vessel D.Lack of oil in the compass bearings
This induced magnetism（）the permanent magnetism already...
单项选择题This induced magnetism（）the permanent magnetism already present in the ship.
A.will add to B.will subtract from C.may add to or subtract from D.will not change
The variation for most given areas undergoes（）change，th...
单项选择题The variation for most given areas undergoes（）change，the amount of which is also noted on charts.
A.an annual B.a constant C.a variable D.an unstable
The quadrantal spheres are used to（）.A.Remove deviation...
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
