Question

Which information is needed to show that a parallelogram is a rectangle?

Answer 1

If a parallelogram has right angles (angles with measures of 90 degrees) for all its angles, it is a rectangle.

Answer 2

If you know for a fact that it's a parallelogram, then you only
need to show that any one angle is a right angle (90 degrees),
and that will prove that it's a rectangle.