## **Core Concept**
The parasympathetic nervous system is a part of the autonomic nervous system that regulates various involuntary functions, including salivation. The salivary glands receive parasympathetic innervation, which stimulates salivation. This innervation is crucial for the regulation of saliva production.

## **Why the Correct Answer is Right**
The correct answer, **C. Facial nerve (VII)**, is right because the facial nerve provides parasympathetic innervation to the submandibular and sublingual salivary glands through the **submandibular ganglion**. The preganglionic parasympathetic fibers originate from the superior salivatory nucleus in the brainstem and travel with the facial nerve. These fibers then synapse in the submandibular ganglion, and postganglionic fibers innervate the submandibular and sublingual glands, stimulating salivation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The **Glossopharyngeal nerve (IX)** does provide parasympathetic innervation, but it is primarily to the **parotid gland**, not the submandibular or sublingual glands, through the **otic ganglion**.
- **Option B:** The **Trigeminal nerve (V)** is primarily involved in sensory innervation of the face and motor innervation of muscles of mastication. It does not provide parasympathetic innervation to the salivary glands.
- **Option D:** The **Vagus nerve (X)** provides parasympathetic innervation to various visceral organs in the thorax and abdomen but not to the salivary glands.

## **Clinical Pearl / High-Yield Fact**
A key clinical correlation is that damage to the facial nerve can result in decreased salivation from the submandibular and sublingual glands, illustrating the importance of the facial nerve in parasympathetic control of salivation.

## **Correct Answer: C. Facial nerve (VII).**