During Descent, an Airplane Passenger Is Complaining That His "Ears

During descent, an airplane passenger is complaining that his "ears are plugged." What aspect of the structure and function of the ear best accounts for the passenger's complaint?

A) The inner ear adjusts its volume in response to atmospheric pressure, increasing during low pressure and decreasing in high pressure.
B) The eustachian tubes must remain patent to equalize pressure between the middle ear and inner ear.
C) The tympanic membrane is selectively permeable in order to accommodate pressure changes, and this capacity is often impaired during upper respiratory infections.
D) Air must be able to flow between the middle ear and nasopharynx in order to accommodate pressure changes.