A.Quadrantal spheresB.Heeling magnetsC.Athwartships mag……

单项选择题Variation is the angular measurement between（）.

A.compass north and magnetic north
B.compass north and true north
C.magnetic meridian and the geographic meridian
D.your vessel's heading and the magnetic meridian

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（）.

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

单项选择题True heading differs from magnetic heading by（）.

A.deviation
B.variation
C.compass error
D.northerly error

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（）.

A.the compass heading is in line with the lubber's line
B.there is no lost motion in the gimbal rings
C.no change of heading by compass is observed if you raise and lower the heeling magnet
D.the gimbal rings do not strike the compass frame when they are tilted