Which of the following is a structure of the upper respiratory tract?

The pharynx is indeed a structure of the upper respiratory tract. It serves as a pathway for both air and food, connecting the nasal cavity to the larynx and the esophagus. The pharynx plays a critical role in helping to warm, humidify, and filter the air we breathe before it moves into the lower respiratory tract.

In contrast, the other structures listed are part of the lower respiratory tract. The trachea is a major airway that extends from the larynx down into the chest, branching into the bronchi, which lead to the lungs. Alveoli are the tiny air sacs in the lungs where gas exchange occurs. The distinction between upper and lower respiratory structures is important in understanding the anatomy and function of the respiratory system as a whole.