Answer with explanation:
The meaning of rotational symmetry is number of times the geometrical shape appear congruent to itself when it is revolved through a complete circle , that is at different angles less than 360°, number of times the Original Shape and Rotated shape Appear congruent to each other , that will be the Rotational Symmetry of the Geometrical shape.
When a Square is rotated by an angle of 90°, at four times it appears congruent to it's Original Shape.
So, Order of Rotational Symmetry of Square =4
