An arrow climbs the board like a staircase, always pointing the way it has just moved. Which board comes next?

The arrow moves one cell at a time, taking turns: right, up, right, up. It points the way it last moved. Its last move was up, so next it moves one cell right, to the right edge of the second row, and points right: (a). (b) goes up twice, (c) points the wrong way and (d) moves diagonally.