If the diagonals of a quadrilateral bisect each other at 90∘, then the quadrilateral is a
In case of rectangle and parallelogram the diagonals bisect each other but not at 90∘
In case of a rhombus and square, the diagonals bisect each other at 90∘.
As we do not know the measure of the interior angle, we conclude the required quadrilateral is a rhombus.
Note: All squares are rhombuses and all rhombuses are not squares.