Which of the following is not a pair of similar polygons?

The answer is the last figure, figure (D). Attached the image.

Step-by-step explanation:  We are given four pairs of polygons and we are to select the pair in which the two polygons are not similar.

In the first pair of polygons, the ratio of the corresponding sides will be same as follows:

So, the polygons are similar.

In the second pair of polygons, the ratio of the corresponding sides will be same as follows:

So, the polygons are similar.

In the third pair of polygons, the ratio of the corresponding sides will be same as follows:

So, the polygons are similar.

In the fourth pair of polygons, we have

and

So, the polygons are not similar in this case.

Thus, the last figure, attached herewith, is the correct option.