Peter justified the SAS Congruence Theorem through this process. The SAS (Side-Angle-Side) Congruence Theorem states that if two triangles have two pairs of congruent sides and the angle between those sides is congruent, then the triangles are congruent. Since the triangles had one pair of congruent angles between two pairs of congruent sides, this setup aligns perfectly with the conditions of the SAS theorem.
Therefore, the correct answer is:
d. The SAS Congruence Theorem