**Core Concept**
The mandibular nerve (a branch of the trigeminal nerve, CN V3) supplies motor innervation to muscles of mastication and associated structures. It does not innervate the buccinator muscle, which is instead supplied by the **buccal branch of the facial nerve (CN VII)**.

**Why the Correct Answer is Right**
The mandibular nerve innervates the masseter, temporalis, and tensor tympani — all muscles of mastication. The buccinator, however, is a facial muscle that elevates the cheek and is innervated by the **facial nerve**, not the trigeminal nerve. This distinction is critical in understanding cranial nerve motor supply and muscle innervation.

**Why Each Wrong Option is Incorrect**
Option B: The masseter is a major muscle of mastication and is directly innervated by the mandibular nerve.
Option C: The tensor tympani, part of the masticatory system, is innervated by the mandibular nerve via the mandibular branch of the trigeminal.
Option D: The temporalis muscle, a key masticator, is supplied by the mandibular nerve through the motor branch of CN V3.

**Clinical Pearl / High-Yield Fact**
Remember: **"Mandibular nerve → mastication muscles; Facial nerve → buccinator."** This is a classic exam trap — students often confuse facial and trigeminal nerve innervation. Always associate the buccinator with the facial nerve (CN VII), not the trigeminal.

✓ Correct Answer: A. Buccinator