单项选择题
Variation is a compass error that you（）.
A.can correct by adjusting the compass card B.can correct by adjusting the compensating magnets C.can correct by changing the vessel's heading D.cannot correct
单项选择题 Variation in a compass is caused by（）.
单项选择题 True heading differs from magnetic heading by（）.
单项选择题 To center a compass bowl in its binnacle，you should have the ship on an even keel，heading north or south，and adjust the screws until（）.
