Which of the following are necessary when proving that the opposite sides of a parallelogram are congruent? Check all that apply. A. Corresponding parts of similar triangles are similar. B. Alternate interior angles are supplementary. C. Alternate interior angles are congruent. D. Corresponding parts of congruent triangles are congruent.,

The opposite sides of a parallelogram can be proved congruent by joining the diagonal of the parallelogram and proving the two triangles congruent by ASA .In any parallelogram opposite sides are parallel.We prove the triangles to be congruent by taking the property of parallel lines that  Alternate interior angles are congruent.When the triangles are proved congruent the opposite sides of parallelogram can be proved equal by using the property Corresponding parts of congruent triangles are congruent.,The options which hold true to prove opposite sides of a parallelogram are congruent are options C and D.C. Alternate interior angles are congruent. D. Corresponding parts of congruent triangles are congruent.,