Which part of the body is associated with equalizing pressure in the middle ear?

The Eustachian tubes are the correct choice because they play a crucial role in equalizing pressure in the middle ear. These tubes connect the middle ear to the back of the throat and allow air to flow in and out of the middle ear, which helps to equalize the pressure on both sides of the tympanic membrane (eardrum). When scuba diving, changes in external pressure can cause discomfort if the pressure in the middle ear does not equalize quickly enough. By opening the Eustachian tubes, divers can alleviate this pressure difference and prevent potential injury to their ears.

The auditory canal is primarily responsible for transmitting sound waves to the tympanic membrane but does not play a role in pressure equalization. The tympanic membrane, or eardrum, is affected by pressure changes and can be damaged if pressure is not equalized properly, but it does not actively equalize pressure itself. The middle ear cavity is the space where the pressure needs to be equalized but, again, does not perform the action of equalization without the Eustachian tubes.