explain why the north and the south poles of a needle always align with North and South poles of Earth respectively?

All magnets have two poles, a north pole and a south pole, and the north pole of one magnet is attracted to the south pole of another magnet and vice-versa. So the compass needle when allowed to spin whichever way it wants, will always line itself along the north-south direction.

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answer: associative property of addition

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