Which term describes the air volume remaining in the lungs after a full exhale?

• A. Tidal Volume
• B. Residual Volume
• C. Vital Capacity
• D. Alveoli

Answer: (B)

Air remaining after a full exhale is called residual volume. This amount stays in the lungs at all times to keep the airways and alveoli inflated, ensuring the lungs don’t collapse and gas exchange can continue. In a typical adult, residual volume is about 1,100–1,200 mL, though it varies with body size and health. The other terms describe different aspects: tidal volume is the amount of air moved in or out during a normal breath, around 500 mL; vital capacity is the total amount that can be exhaled after a maximal inhalation, about 4,800 mL; and alveoli are the tiny air sacs where oxygen and carbon dioxide exchange, not a volume.