**Core Concept**
Frey's syndrome, also known as gustatory sweating or auriculotemporal syndrome, is a rare neurological disorder characterized by excessive sweating and flushing of the skin in response to stimuli that would normally cause salivation, such as seeing or smelling food. This condition is caused by aberrant regeneration of nerve fibers between the parotid gland and the overlying skin, leading to an abnormal connection between the sympathetic and parasympathetic nervous systems.

**Why the Correct Answer is Right**
The correct answer is **C. Auriculotemporal nerve**. This nerve, a branch of the mandibular division of the trigeminal nerve, carries parasympathetic fibers from the otic ganglion to the parotid gland. Damage to this nerve, often due to surgery in the parotid gland region, can lead to aberrant regeneration of nerve fibers and the development of Frey's syndrome. The aberrant regeneration leads to an abnormal connection between the sympathetic fibers, which cause sweating, and the parasympathetic fibers, which cause salivation.

**Why Each Wrong Option is Incorrect**
**Option A:** The glossopharyngeal nerve carries parasympathetic fibers to the parotid gland, but damage to this nerve does not typically result in Frey's syndrome.

**Option B:** The facial nerve controls facial expressions and taste, but it is not directly involved in the development of Frey's syndrome.

**Option D:** The vagus nerve is a major parasympathetic nerve that supplies various organs, but damage to this nerve is not typically associated with Frey's syndrome.

**Clinical Pearl / High-Yield Fact**
Frey's syndrome is often seen after parotid surgery, such as parotidectomy for parotid tumors. It's essential to preserve the auriculotemporal nerve during such surgeries to prevent the development of Frey's syndrome.

**Correct Answer:** C. Auriculotemporal nerve