During expiration, what happens to the diaphragm?

• A. It contracts and moves downward
• B. It remains contracted
• C. It expands outward
• D. It relaxes and moves upward

Answer: (D)

During expiration, the diaphragm relaxes and moves upward into a dome shape, which reduces the thoracic cavity’s volume and increases pressure to push air out of the lungs. In normal breathing, expiration is mostly a passive process driven by the lungs’ elastic recoil, so the diaphragm returns to its relaxed position and rises. The contraction and downward movement of the diaphragm describe inhalation, not expiration, and the other options don’t reflect the upward relaxation pattern that drives exhalation.