**Core Concept**
The sense organ for hearing is responsible for detecting vibrations in the air and transmitting these signals to the brain, allowing us to perceive sound. This process involves the conversion of mechanical energy into electrical signals. The organ consists of a complex structure with sensory hair cells, supporting cells, and a fluid-filled space called the scala media.

**Why the Correct Answer is Right**
The correct answer is the cochlea, a spiral-shaped structure in the inner ear. The cochlea houses the sensory hair cells, which are embedded in the basilar membrane and respond to vibrations in the fluid. When sound waves reach the cochlea, they cause the fluid to vibrate, bending the hair cells and triggering an electrical signal that is transmitted to the auditory nerve and ultimately to the brain. This process is mediated by the mechanoreceptors in the hair cells, which are sensitive to movement and changes in fluid pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** The auditory nerve is responsible for transmitting electrical signals from the cochlea to the brain, but it is not the sense organ itself.
**Option B:** The eardrum is a critical structure in the hearing process, but it is not the sense organ; rather, it is a membrane that transmits vibrations from the air to the middle ear bones.
**Option C:** The vestibular system is responsible for balance and equilibrium, not hearing.

**Clinical Pearl / High-Yield Fact**
The cochlea is a highly specialized structure that is responsible for converting sound waves into electrical signals. Damage to the cochlea, such as noise-induced hearing loss or age-related hearing loss, can result in permanent hearing impairment.

**Correct Answer: C. Cochlea**