What is the biconditional statement of the following conditional statement?

"If a polygon has five sides, then it is a pentagon."

If a polygon does not have five sides, then it is a not pentagon.
If a polygon is not a pentagon, then it is does not have five sides.
If a polygon is a pentagon, then it has five sides.
A polygon has five sides if and only if it is a pentagon.

A polygon has five sides if and only if it is a pentagon.