Answer: External auditory canal
Explanation: External auditory canal or external acoustic meatus is a passage that leads from the outside head to the eardrum of ear.
The structure of external auditory canal is same in all the mammals, slightly curved tube extending from the outer ear towards eardrum.
This canal is almost 2.5 cm in length with some hairs and sweat glands on the outer side to prevent insects from entering into the ear.
So, the correct answer is external auditory canal.
