Final answer:
Having four right angles is a sufficient condition to conclude that a quadrilateral is a square.
Step-by-step explanation:
The condition that is sufficient to conclude that a quadrilateral is a square is having four right angles (option A). In a square, all four angles are equal and measure 90 degrees. This is because a square is a special type of rectangle, and all rectangles have four right angles. Therefore, if a quadrilateral has four right angles, it is a square.