The correct option is
B infinitely many sides
Polygon is a shape of a finite number of sides, whereas a circle is an infinite gon.
Consider the following example:
The left-most figure is a polygon of 7 sides, and the middle figure is a polygon of 12 sides.
∴ When the number of sides of a polygon increase, the shape tends to become a circle.
However, a circle is formed only when the number of sides is infinite.