which of the following are not necessary when proving that the diagonals of a rectangle are congruent? check all that apply

A quadrilateral is called rectangle if the opposite sides are congruent and parallel to each other. All interior angles are right angle and congruent.

To prove that the diagonals of a rectangle are congruent the necessary conditions are

1. Opposite sides of a rectangle are congruent.

2. All right angles are congruent.

Therefore options A and C are necessary conditions. Option A and C are incorrect.

The opposite sides of a rectangle are parallel to each other and two parallel lines never intersect each other.

Therefore the opposite sides are not perpendicular to each other. Option D is correct.

The angle whose measure is more than 90 degree is called an obtuse angle.

Since all interior angles of a rectangle are right angle and congruent, therefore there is no obtuse angle. So, condition B is unnecessary. Option B is correct.