Which structure is part of the lower respiratory tract?

• A. Trachea
• B. Bronchi
• C. Pharynx
• D. Nasal cavity

Answer: (B)

The main idea is separating the airway into upper and lower parts. The upper respiratory tract includes structures like the nasal cavity and pharynx that condition air before it moves deeper. The lower respiratory tract consists of the airways within the lungs that carry air onward toward the gas-exchange zones, such as the trachea and the bronchial tree. The bronchi are the branches that continue from the trachea and dive into each lung, forming the major conduits that deliver air to the smaller airways and eventually to the alveoli. Because they reside inside the lungs and are a key part of moving air down to the sites of gas exchange, bronchi are part of the lower respiratory tract. The nasal cavity and pharynx are upper airway structures, and while the trachea is also a lower airway, the bronchi are the clear example of a lower-respiratory structure among the options.