**Core Concept**
The organ of Corti is a critical auditory organ located within the cochlea of the inner ear, responsible for converting mechanical sound waves into electrical signals transmitted to the brain. It is a highly specialized structure composed of sensory hair cells, supporting cells, and a basement membrane.

**Why the Correct Answer is Right**
The organ of Corti is indeed situated on the basilar membrane, a flexible, gelatinous structure that runs along the length of the cochlea. The basilar membrane vibrates in response to sound waves, causing the sensory hair cells to bend and generate electrical signals. This process is essential for sound processing and perception. The organ of Corti is embedded within the scala media, a compartment of the cochlea that is filled with a fluid called endolymph, and is in close proximity to the basilar membrane.

**Why Each Wrong Option is Incorrect**
**Option B:** The utricle is one of the otolith organs in the vestibular system, responsible for detecting linear acceleration and changes in head position. It is not related to the organ of Corti or sound processing.
**Option C:** The saccule is another otolith organ in the vestibular system, involved in detecting linear acceleration and changes in head position. Like the utricle, it is not associated with the organ of Corti or sound processing.
**Option D:** This option is incorrect because the organ of Corti is indeed located on the basilar membrane, making one of the above options correct.

**Clinical Pearl / High-Yield Fact**
The organ of Corti is a highly specialized structure that is susceptible to damage from loud noises, certain medications, and age-related degeneration. Understanding its anatomy and function is crucial for diagnosing and managing hearing-related disorders.

**✓ Correct Answer: A. Basilar membrane**