Answer:
Equalized air pressure.
Explanation:
The function of eustachian tube enables air pressure to be equalized between the outside air and the middle ear cavity. The eustachian tube also known as pharyngotympanic tube that connects the middle ear cavity with the nasopharynx. Eustachian tube is responsible for the aeration of the middle ear system as well as clears mucus from the middle ear into the nasopharynx. Opening and closing functions of the eustachian tube are is very important.
