How could you use coordinate geometry to prove that segment BC is congruent to segment AD?

Figure ABCD is shown. A is at negative 3, 2. B is at 0, 6. C is at 6, 6. D is at 3, 2.

A. Prove the slopes are the same.
B. Prove the slopes are opposite reciprocals.
C. Prove the lengths are the same.
D. Prove the midpoints are the same.