Which of the following describes the volume of air moved in a normal breathing cycle?

• A. Inspiratory Reserve Volume
• B. Residual Volume
• C. Tidal Volume
• D. Expiratory Reserve Volume

Answer: (C)

Tidal volume is the amount of air moved during a normal, quiet breath. In a healthy adult, this is about 500 mL per breath and represents the air exchanged with the atmosphere during resting breathing—inhaled and then exhaled.

The other volumes describe air beyond a typical breath: inspiratory reserve volume is the extra air you could inhale with a deep breath after a normal inhalation; expiratory reserve volume is the extra air you could push out after a normal exhalation; residual volume is the air left in the lungs after a maximal exhale and cannot be expelled. Since the question focuses on the air moved in a normal breathing cycle, tidal volume is the best description.