Which of the following is NOT a branch of the mandibular (V3) nerve?

The correct answer is rooted in the anatomical classification of the branches of the mandibular nerve, which is the third division of the trigeminal nerve (V). The branches of the mandibular nerve include the auriculotemporal nerve, the lingual nerve, and the inferior alveolar nerve, all of which arise from this division.

The auriculotemporal nerve primarily supplies sensory innervation to the external ear and parts of the temporal region. The lingual nerve provides sensation to the anterior two-thirds of the tongue and also carries taste fibers from the chorda tympani. The inferior alveolar nerve gives rise to sensory innervation for the lower teeth.

In contrast, the infraorbital nerve is not a branch of the mandibular nerve; rather, it branches off from the maxillary nerve (V2), which is the second division of the trigeminal system. The infraorbital nerve innervates the skin of the upper lip, lower eyelid, and part of the nasal cavity. Therefore, identifying the infraorbital nerve as not part of the mandibular nerve makes clear why this option is the correct choice in the question.