Three of the panels show this tile in a mirror placed along one of its sides or diagonals. Which panel is the odd one out?

Check the turning sense: going round from the yellow cell to the arrow to the dot, a mirror image must go the opposite way round. (b), (c) and (d) do, so they are mirror images. (a) goes round the same way as the tile: it is the tile turned a quarter-turn, not reflected.