Q. If $ABCD$ be a parallelogram and $M$ be the point of intersection of the diagonals. If $O$ is any point, then $ \overset{\to }{\mathop{OA}}\,+\overset{\to }{\mathop{OB}}\,+\overset{\to }{\mathop{OC}}\,+\overset{\to }{\mathop{OD}}\, $ is
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