Concept:The mammalian ear has two main functional roles: hearing and the maintenance of balance, carried out by distinct parts of the inner ear.
Explanation:The cochlea is the part of the inner ear responsible for hearing only.
The pinna is the outer, visible part of the ear that collects sound waves.
The perilymph is a fluid that fills parts of the inner ear and helps transmit vibrations, but it does not control balance.
The vestibular system, which includes the semicircular canals and the vestibule, detects head position and movement.
Sensory receptors in the vestibular system send signals to the brain to help maintain posture and balance.
Damage or disturbance of the vestibular system can cause dizziness and loss of equilibrium.
Therefore, among the given options, the structure responsible for maintaining balance is the vestibular system.
Answer:D. vestibular system