单项选择题
The principal purpose of adjustment of the magnetic compass is to eliminate（）as far as possible.
A.variation B.compass error C.deviation D.earth‟s magnetic force
单项选择题 You are standing the wheelwatch on entering port and the master gives you a rudder command which conflicts with a rudder command from the pilot.What should you do?（）
单项选择题 （）is used for lifting cargo.
单项选择题 The original equilibrium position is stable when（）.
