<em><u>Polygon:</u></em> a figure formed by coplanar segments
with one distinct interior region
Figure A, Figure B, and Figure D would be considered polygons.
Notice that those figures I mentioned above are
composed of line segments, and nothing else.
In addition, these figures don't have two separate
interior regions and figures that do aren't polygons.
Figure C would not be a polygon because
it's formed by a curve rather than line segments.
