Each dial has one orange hand. The hand turns by one fixed amount from cell to cell along a row and by another fixed amount down a column. Which dial is missing?

Along each row the hand turns $45^{\circ }$ clockwise (up, upper-right, right); down each column it turns $90^{\circ }$ clockwise (up, right, down). The last dial is the one above it turned $90^{\circ }$ further: from down to left, which also equals the one to its left (down-left) turned $45^{\circ }$: (d). (b) repeats its left neighbour, (a) and (c) point the wrong way.