## **Core Concept**
The question tests knowledge of cranial nerves, specifically their functional classification. Cranial nerves can be purely sensory, purely motor, or mixed. Purely sensory nerves are responsible for transmitting sensory information from the body to the brain.

## **Why the Correct Answer is Right**
The correct answer, **CN VIII (Vestibulocochlear nerve)**, is a pure sensory nerve. It is responsible for transmitting sound and balance information from the cochlea and vestibular apparatus of the inner ear to the brain. This nerve does not have any motor functions.

## **Why Each Wrong Option is Incorrect**
* **Option A: CN III (Oculomotor nerve)** - This is a purely motor nerve, responsible for controlling the movement of the eye muscles, constriction of the pupil, and maintaining the eyelid open.
* **Option B: CN V (Trigeminal nerve)** - This is a mixed nerve, providing sensory innervation to the face and motor innervation to the muscles of mastication.
* **Option D: CN X (Vagus nerve)** - This is also a mixed nerve, providing both sensory and motor innervation to various organs in the thorax and abdomen.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that there are only two purely sensory cranial nerves: **CN I (Olfactory nerve)** and **CN VIII (Vestibulocochlear nerve)**. This fact can help in quickly identifying the correct answer in questions related to the classification of cranial nerves.

## **Correct Answer:** . VIII. Vestibulocochlear nerve