Look at the shape and at the dots inside it. Both change from one box to the next. Which box completes the series?

The shape loses one side each time (hexagon, pentagon, square) while the number of dots inside goes up by one (0, 1, 2). Next comes a triangle with 3 dots: (c). (a) forgets the extra dot, (b) keeps the square and (d) is not a triangle.