**Core Concept**
Aminoglycoside antibiotics cause ototoxicity, specifically affecting the cochlea in the inner ear. This damage leads to sensorineural hearing loss, which is characterized by difficulty in perceiving high-frequency sounds.

**Why the Correct Answer is Right**
Aminoglycosides exert their ototoxic effects on the outer hair cells of the cochlea, particularly those located in the basal (lower) turn. These outer hair cells are responsible for amplifying sound vibrations, allowing for the detection of high-frequency sounds. When aminoglycosides bind to the calcium channels on the outer hair cells, they disrupt the normal functioning of these cells, leading to their damage and subsequent hearing loss.

**Why Each Wrong Option is Incorrect**
**Option A:** Inner hair cells are responsible for transmitting sound signals to the auditory nerve, but they are not the primary target of aminoglycoside-induced ototoxicity.
**Option C:** The apical (upper) turn of the cochlea is involved in detecting low-frequency sounds, which are not typically affected by aminoglycoside ototoxicity.
**Option D:** While outer hair cells in the apical turn may be affected by ototoxicity, the basal turn is the primary site of damage caused by aminoglycosides.

**Clinical Pearl / High-Yield Fact**
Aminoglycoside-induced hearing loss is usually irreversible and can be detected through audiometric tests. It is essential to monitor patients receiving aminoglycoside therapy for signs of ototoxicity, such as tinnitus or decreased hearing acuity.

**✓ Correct Answer: B. Outer hair cells of basal turn**