The violet L-shape turns by a different amount at alternate steps. Which figure comes next?

The turns alternate: $90^{\circ }$ clockwise, then $45^{\circ }$ clockwise, then $90^{\circ }$ clockwise again. So the next turn is $45^{\circ }$ clockwise, which stands the long arm upright on the right with the short arm along the bottom pointing left: (c). (a) turns $90^{\circ }$ again, (d) turns back anticlockwise and (b) is a mirror image, which no turn can produce.