**Core Concept**
The stapedial reflex, also known as the acoustic reflex, is an **involuntary reflex** that occurs in response to loud sounds. It involves the **stapedius muscle**, which is innervated by the **facial nerve (VII)**, and the **cochlea**, which is innervated by the **vestibulocochlear nerve (VIII)**.

**Why the Correct Answer is Right**
The stapedial reflex is mediated by the **facial nerve (VII)**, which controls the stapedius muscle, and the **vestibulocochlear nerve (VIII)**, which transmits sound signals from the cochlea. An absence of the stapedial reflex can indicate a problem with either of these nerves. A lesion in the **VIII nerve** would disrupt the afferent pathway of the reflex, preventing the reflex from occurring.

**Why Each Wrong Option is Incorrect**
**Option A:** Otosclerosis is a condition that affects the middle ear, specifically the **ossicles**, and can cause hearing loss, but it does not directly affect the stapedial reflex.
**Option B:** X nerve lesion refers to a lesion of the **vagus nerve**, which is not directly involved in the stapedial reflex.
**Option D:** V nerve lesion refers to a lesion of the **trigeminal nerve**, which is also not directly involved in the stapedial reflex.

**Clinical Pearl / High-Yield Fact**
The stapedial reflex is an important diagnostic tool in **hearing assessment** and **neurological evaluation**. Its absence can indicate a range of conditions, from simple middle ear problems to more complex neurological disorders.

**Correct Answer:** C. VIII nerve lesion