In the proof that the diagonals of rectangle ABCD are congruent, after the statements that \( AD \cong BC \), \( AB \cong AB \) (reflexive property), and \( \angle DAB \cong \angle CBA \), the next logical step would typically be:
d. triangle DAB ≅ triangle AOB
This is because you would be using the Side-Angle-Side (SAS) congruence postulate to show that triangles DAB and AOB are congruent, leading towards proving that the diagonals AC and BD are equal.