The correct answer is option A. auditory canal, eardrum, ossicles, cochlea
The sound travel as waves through the auditory canal, trigger the eardrum to vibrate. This causes the three small bones called ossicles, in the middle ear to move. The vibrations move along the fluid in the cochlea in the inner ear, triggering thousands of small hair cells.
This results in the change of the vibrations into electrical impulses.These impulses finally recognized by the brain.
Thus, the correct option would be option a.