**Core Concept**
Streptomycin, an aminoglycoside antibiotic, is well-known for its ototoxic potential, causing damage to the inner ear. This ototoxicity is a significant side effect that can lead to hearing impairment, including deafness and tinnitus.

**Why the Correct Answer is Right**
Streptomycin's ototoxicity is primarily due to its ability to bind to the hair cells in the cochlea, disrupting the normal functioning of these cells. This leads to damage to the vestibulocochlear nerve, resulting in symptoms such as hearing loss and tinnitus. Streptomycin's ototoxic effects are more pronounced in the higher frequencies and are often irreversible. The vestibulocochlear nerve, responsible for transmitting sound and balance information, is particularly vulnerable to damage from aminoglycoside antibiotics like streptomycin.

**Why Each Wrong Option is Incorrect**
**Option B:** Isoniazid is primarily associated with peripheral neuropathy, hepatitis, and other side effects, but ototoxicity is not a common or notable side effect of this medication.
**Option C:** Ethambutol is known for its potential to cause optic neuritis, leading to visual disturbances, but it is not associated with ototoxicity.
**Option D:** Rifampicin is generally well-tolerated and not known for causing ototoxicity or hearing loss.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that aminoglycoside antibiotics, including streptomycin, require careful monitoring of renal function and ototoxicity, as these side effects can be irreversible.

**Correct Answer Line**
✓ Correct Answer: A. Streptomycin