Answer:
D. The auditory tube drains into the nasopharynx.
Explanation:
The auditory tubes, commonly known as eustachian tubes have their pharyngeal openings in the lateral wall of the nasopharynx. Auditory tubes also prevent the mucus to enter the middle ear by channelizing it into the nasopharynx. This clearance of mucus does not allow any infection to spread to the middle ear.