1. Which of the following is a key feature that distinguishes a square from other quadrilaterals?
All sides are equal in length and all angles are right angles
Explication
A square is uniquely characterized by having all sides equal in length and all interior angles equal to 90 degrees. This distinguishes it from other quadrilaterals, such as rectangles (which require right angles but not all sides equal), rhombuses (which have all sides equal but angles are not necessarily right angles), or irregular quadrilaterals. The other options either describe properties of other shapes or are incomplete.