Answer: Option D.
Explanation:
Outer ear is the external part of ear called pinna with a helical shape.
Pinna helps in collecting sound waves and guide them to the eardrum.
The pinna helps in assisting the difference in pressure inside and outside the ear. Pinna function sin resisting the high pressure of sound waves inside the ear and makes the smoother sound to transmit which passes into the auditory canal.
Hence, the correct option is D.
