In parallelogram abcd, angle d is a right angle. determine whether the parallelogram is a rectangle. if so, by what property

Yes, the parallelogram is a rectangle. We know one of the properties of a parallelogram is that opposite angles are the same. If angle D is is a right angle, then the rest of the angles should also be right angle (since the opposite angle would be 90 and lead to the rest of the angles to become 90 as well).

Hope I helped :)