Please help quickly on math question related to geometry

Question

Scott wants to make sure that the window he is buying is a rectangle. He has measured the window and knows that the opposite sides are congruent. Of the following choices, what piece of information would prove that the window is indeed a rectangle?

image provided: https://ibb.co/dbD5cmg

Answer choices

a	m∠A + m∠C = 180°
b	∠A ≅ ∠D
c	Diagonal AD ≅ Diagonal BC
d	None of these will prove the window is a rectangle.
e	Diagonal AD ⊥ Diagonal BC

Answer: _

Answer 1

ABCD is a parallelogram because opposite sides are equal. A parallelogram is a rectangle if and only if its diagonals are congruent. Only choice c satisfies that requirement.