By definition, a rectangle is a four-sided figure with four right-angle corners. Which of these expresses this definition as a biconditional statement?

A .A quadrilateral is a rectangle iff it has four 90º angles.

B. Once a quadrilateral has four 90º angles it has become a rectangle.

C. Quadrilaterals are rectangles when they have four 90º angles.

D. A rectangle is a quadrilateral with four 90º angles.