A dome shaped muscle that inflates the lungs allowing breathing

• A. Larynx
• B. Epiglottis
• C. Nasal passage
• D. Diaphragm

Answer: (D)

Breathing relies on the diaphragm, a dome-shaped muscle that forms the floor of the thoracic cavity. When it contracts, it pulls downward and flattens, expanding the chest vertically and increasing the volume inside the thorax. This drop in pressure inside the lungs draws air in, inflating them. When the diaphragm relaxes, it arches back up, helping push air out.

This muscle is central to inspiration, unlike the other structures listed. The larynx is part of the airway and voice box, not a muscle that inflates the lungs. The epiglottis is a flap that protects the airway during swallowing. The nasal passages are routes for air entry that warm and filter air but don’t actively inflate the lungs.