Which of the following represents a polygon with three sides?

A polygon with three sides is known as a triangle. This is a fundamental concept in geometry where polygons are defined based on the number of sides they have. Each polygon type has its own specific number of sides: a triangle has three, a quadrilateral has four, a pentagon has five, and a hexagon has six. The defining characteristic of a triangle is its three vertices connected by three edges, forming the simplest closed figure in a plane. This makes it the sole correct choice when identifying a polygon specifically with three sides.