Step 1: Understanding the Concept:
Lung capacity is split into four basic volumes by spirometry, and the question wants the one that corresponds to a single normal breath, not a forced or reserve volume.
Step 2: Key Concept or Approach:
Recall how the four primary lung volumes are defined: tidal volume covers normal breathing, while inspiratory reserve volume, expiratory reserve volume and residual volume all describe air linked to forced breathing or air that cannot be exhaled at all.
Step 3: Detailed Explanation:
During quiet breathing, a person breathes in and out roughly 500 mL of air with each cycle; this is the tidal volume.
Inspiratory reserve volume is the additional air pulled in only during a deep, forced breath, so it plays no part in a normal cycle.
Expiratory reserve volume is the additional air pushed out only during forced expiration, again not part of a resting breath.
Residual volume stays trapped in the lungs after maximum expiration and is never moved in or out at all.
Since only tidal volume is exchanged with every single breath, it is the volume the question is describing.
Step 4: Final Answer:
The air moved in or out of the lungs with each respiratory cycle is the tidal volume.