Concept:Expiration involves changes that reduce the thoracic cavity volume to push air out.Explanation:During expiration, the intercostal muscles relax, the ribs move downwards and inwards, and the sternum moves inward.These actions decrease the thoracic cavity volume.The thoracic cavity does not first increase in volume during expiration; it actually decreases.Therefore, the statement "the thoracic cavity first increases in volume" is not part of expiration.Answer:B. The thoracic cavity first increases in volume.