answer: your correct answer is b. d.
D + B
(CPCTC + opposite sides are congruent)
If you take the rectangle with the geometric center O. Match the sides of opposite triangles. AB will be equal to CD and AC is equal to BD. Angles AOB is equal to the angle COD and angle AOC is equal to angle BOD.
The two diagonals bisect each other and therefore each all parts of the diagonal are equal.
Therefore the two diagonals are congruent.
Opposite sides are congruent; All right angles are congruent
B. Corresponding parts of congruent triangles are congruent