Which of the following best describes the figure?
a. convex octagon
b. regular octagon
c. concave octagon
d. not a polygon
![Which of the following best describes the figure a convex octagon b regular octagon c concave octagon d not a polygon class=](https://us-static.z-dn.net/files/d1c/89d1ce6f8da13ce8169175df64a6c35d.jpg)