What is the basic function of the outer ear?
a. to filter out high-intensity sound waves that can be harmful
b. to amplify low-intensity sounds to detectable levels
c. to protect the hair cells
d. to concentrate and funnel sound waves to the eardrum
e. to filter out low-intensity sound waves that can be harmful.

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.

c. establishing proper sleep hygiene

c. is the correct answer