单项选择题
A.variation
B.deviation
C.variation and deviation
D.a correction for the direction of current set
单项选择题 When adjusting a magnetic compass using the fore-and-aft permanent magnets，you should（）.
单项选择题 When adjusting a magnetic compass for error，a deviation table should be made（）.
单项选择题 When a vessel changes course from one cardinal heading to another cardinal heading whilea djusting the compass，which action should be taken?（）