**Core Concept**
The facial nerve (cranial nerve VII) provides motor innervation to the muscles of facial expression and carries parasympathetic fibers to salivary glands, including the submandibular gland. It exits the skull via the stylomastoid foramen and runs through the parotid gland, then descends to innervate the submandibular gland via its branch to the submandibular salivary gland.

**Why the Correct Answer is Right**
The facial nerve (CN VII) gives off a branch that supplies the submandibular gland, specifically the submandibular salivary gland, via the submandibular nerve (a branch of the mandibular division of the trigeminal nerve). This branch is a continuation of the facial nerve, which runs in the submandibular space and innervates the gland. The parasympathetic fibers from the facial nerve stimulate acinar secretion in this gland.

**Why Each Wrong Option is Incorrect**
Option A: The lingual nerve, a branch of the mandibular division of the trigeminal nerve, provides sensory innervation to the floor of the mouth and lingual mucosa, not motor to the submandibular gland.
Option B: The hypoglossal nerve (CN XII) innervates the intrinsic muscles of the tongue and does not serve the submandibular gland.
Option C: The glossopharyngeal nerve (CN IX) innervates the parotid gland and the pharynx, not the submandibular gland.

**Clinical Pearl / High-Yield Fact**
Remember: The facial nerve supplies **parasympathetic** fibers to the **submandibular** and **sublingual** glands, while the **glossopharyngeal** nerve supplies the **parotid** gland. This distinction is critical in understanding salivary gland innervation and nerve injuries.

✓ Correct Answer: D. Facial nerve