Which drawing shows this stack seen from the right-hand side, in the direction of the arrow marked Side?

Seen from the right, the front row is on your left and the back row on your right. The tallest stack in each row: front row 1, middle row 3, back row 2. So the view is 1, 3, 2: (c). (a) is the same view reversed, and (b) is the view from the front.