## Core Concept
Unilateral sensorineural hearing loss refers to a condition where there is damage to the inner ear or the auditory nerve pathway on one side, leading to hearing loss. This type of hearing loss can result from various causes, including infections, trauma, tumors, or vascular events affecting the auditory system.

## Why the Correct Answer is Right
The correct answer, **C. Acoustic neuroma**, is right because acoustic neuroma, also known as vestibular schwannoma, is a benign tumor that grows on the cranial nerve running from the brain to the inner ear. This tumor affects the nerve responsible for balance and hearing, leading to unilateral sensorineural hearing loss. The growth of the tumor can compress or damage the auditory nerve, resulting in hearing loss on the same side as the tumor.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because while otosclerosis can cause hearing loss, it typically results in conductive hearing loss rather than sensorineural hearing loss. Otosclerosis involves abnormal bone growth in the middle ear that can cause fixation of the stapes bone, leading to a conductive hearing loss.
- **Option B:** This option is incorrect as it does not directly relate to a known cause of unilateral sensorineural hearing loss. Without a specific condition listed, it's hard to directly refute, but common causes include those affecting the inner ear or auditory nerve directly.
- **Option D:** This option is incorrect because while infections can cause hearing loss, they more commonly result in conductive hearing loss (e.g., otitis media) or, if severe, sensorineural hearing loss, but typically not unilateral unless specifically affecting one ear.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **acoustic neuroma** is a classic cause of unilateral sensorineural hearing loss. Patients with acoustic neuroma may also present with tinnitus (ringing in the ears) and balance problems. Early diagnosis and treatment are crucial to prevent further complications.

## Correct Answer: C. Acoustic neuroma.