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When adjusting a magnetic compass using the fore-and-aft permanent magnets，you should（）.
A:use the magnets one at a time，putting one in one side and then one on the opposite side，one step higher
B:use the magnets in pairs，starting at the top，with trays at the highest point of travel
C:use the magnets in pairs，from the bottom up，with the trays at the lowest point of travel
D:fill all the trays with magnets，then remove them one-by-one until the deviation is removed

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出自：海船船员证

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