Theorem: If the diagonals of a parallelogram are congruent, then each angle of the parallelogram is a right angle.
Kim is writing the proof of the theorem using the properties of a parallelogram shown below.
• The opposite sides of a parallelogram are parallel.
• The opposite sides of a parallelogram are congruent.
A parallelogram ABCD with diagonals AC and BD.
She proved the theorem by showing that triangle ADC is congruent to triangle CBA using the _________ Postulate.

I think its SSS....
• The opposite sides of a parallelogram are parallel.
• The opposite sides of a parallelogram are congruent.
they are both talking about sides.............

nvr mind, I found the angle
Theorem: If the diagonals of a parallelogram are congruent, then each angle of the parallelogram is a right angle.
So I concure with them lol