The correct answer is:
Mario has shown that the two triangles are congruent. Three transformations are not always necessary when moving one triangle on top of the other.
Explanation:
Mario successfully translated and rotated triangle \( \triangle ABC \) to coincide with triangle \( \triangle LMN \), demonstrating that \( \triangle ABC \) and \( \triangle LMN \) are congruent. Congruence can be established through various sequences of transformations, and it is not strictly necessary to have one of each type (translation, rotation, reflection) to prove congruence. In this case, the translation followed by the rotation was sufficient to show that the two triangles overlapped exactly, indicating they are indeed congruent.