单项选择题
Compass deviation is caused by（）.
A.magnetism from the earth's magnetic field B.misalignment of the compass C.magnetism within the vessel D.a dirty compass housing
单项选择题 Compass error is equal to the（）.
单项选择题 Deviation in a compass is caused by the（）.
单项选择题 Deviation is the angle between the（）.
