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 （）the repeater compass with the master compass，please.
单项选择题 My gyro-compass error is（）.
单项选择题 There is a possibility that small vessel，ice and other floating objects may not be（）by radar at an adequate range.
