Which of the following is NOT part of the lower airway?

• A. Nasal cavity
• B. Lungs
• C. Trachea
• D. Bronchioles

Answer: (A)

Airways are usually divided into upper and lower sections. The nasal cavity lives in the upper airway, along with the mouth, pharynx, and larynx, and it mainly filters, warms, and humidifies air before it progresses downward. The lower airway begins after the larynx and includes the trachea, bronchi, bronchioles, and the gas‑exchange regions within the lungs. So the nasal cavity does not belong to the lower airway, making it the correct choice. The other parts—trachea, bronchioles, and the lungs—are all part of the lower airway system.