Which box is next in the sequence?

The correct answer is:

In the question there is an image with some patterns on it using which we have to find the next sequence of the pattern.
From the image we can say that,
The last polygon of the given image has 3dots inside it, and the polygon itself has 4 sides.
So, from our observation we can say that, the next figure must have 2 dots inside it, and the polygon will have 3 sides.
Thus, the figure will be a triangle with 2 dots inside it.
Therefore, the correct option is (a).