The formal definition of a polygon states that a polygon is a closed plane figure formed by or more segments called sides. each side intersects exactly two other noncollinear sides, one at each endpoint.

a. four
b. one
c. zero
d. two
e. three

The answer would be three. The reasons are clear. You can't form a closed figure when you just have two sides. All they would do is just intersect each other. Also, one side must intersect with two other noncollinear sides. This means that a polygon has to have at least three sides. 

Its equal to d=7.07in