Answer:
A parallelogram with congruent diagonals, a parallelogram with a right angle, a parallelogram with perpendicular diagonals.
Explanation:
By definition, a rectangle is nothing but a parallelogram with one right angle. One of the properties of a rectangle is that its perpendiculars are congruent. Finally, the diagonals of a rectangle are congruent (this can be proved by finding congruent triangles split by the diagonals, using CPCTC, etc.).