The correct option is A ∣∣∣[→a,→b,→c]∣∣∣∣∣∣→a×→b+→b×→c+→c×→a∣∣∣
The vector equation of the plane passing through points →a,→b,→c is
r.(→a×→b+→b×→c+→c×→a)=[→a,→b,→c]
Therefore, the length of the perpendicular from the origin to this plane is given by
∣∣∣[→a,→b,→c]∣∣∣∣∣∣→a×→b+→b×→c+→c×→a∣∣∣