My answer to this question is A. The heptagon has seven sides and the decagon has 10 sides. Since the sides just have to be added together, that will be 7 + 10 = 17. There are a lot of people who like polygons because they are amazed by the number of sides that are available.
The number of available polygons has also increased steadily over the past years. Most people are familiar with the usual polygons but there are now polygons that are considered to be complex or even irregular. The polygons right now do not need to have equal shapes. They just need to have different sides in order to be called a polygon.