Are stimulated when sound waves vibrate hair cells in the inner ear

Out of the following choices;

A. mechanoreceptors. B. thermoreceptors. C. photoreceptors. D. nociceptors.

The answer is A. Intuitive as the name suggest, the receptors respond to physical or mechanical pressure and distortion. They detect when the hairs change position, even the slightest movement. This way they convert the mechanical energy from the sound waves to the electrical impulse to the brain.