Question

decagon
pentagon
heptagon
nonagon
above has 9 sides. it is an equilateral (but not equiangular)

Explanation:

Step1: Recall polygon names

A decagon has 10 sides, a pentagon has 5, a heptagon has 7, and a nonagon has 9.

Step2: Match side count

The figure has 9 sides, so it's a nonagon.

Answer:

nonagon (from the options: nonagon)