Which characteristic applies to a square?

A square is defined as a specific type of quadrilateral that possesses a few key characteristics. Firstly, all four sides of a square are of equal length, which means that the sides are congruent. This equality of the sides is one of the fundamental properties that distinguishes a square from other quadrilaterals. Secondly, a square has four right angles, making each angle measure exactly 90 degrees. The combination of congruent sides and right angles leads to the classification of a square as a regular quadrilateral, meaning it is both equilateral and equiangular.

This choice captures the essence of a square's geometry, as it encompasses both of these defining features. The presence of congruent sides ensures symmetry, while the right angles guarantee that the shape adheres to the definition of a rectangle as well. Hence, this option provides a complete and accurate description of a square.