Wheel A becomes wheel B. Apply the same change to wheel C, which has two shaded parts.

In B the shaded part has jumped to the opposite side of the wheel (half a turn) and changed from orange to blue. In C the orange part on the upper left therefore becomes a blue part on the lower right, and the blue part on the upper right becomes an orange part on the lower left: (a). (b) only swaps the colours, (c) moves the parts without swapping colours and (d) moves only one part.