Which organ is used for breathing?

• A. Heart
• B. Brain
• C. Lungs
• D. Liver

Answer: (C)

Breathing relies on the lungs as the primary site of gas exchange. Air travels down the airway to the tiny alveoli in the lungs, where oxygen passes into the blood and carbon dioxide moves from the blood into the air to be exhaled. This exchange is driven by ventilation, helped by the diaphragm and intercostal muscles that expand and contract the chest cavity to pull air in and push it out. Among the options, the lungs are the organ that actually performs this gas exchange, making them the correct choice. The heart circulates blood but isn’t involved in exchanging gases; the brain regulates breathing but doesn’t directly exchange oxygen and carbon dioxide; the liver handles metabolism and detoxification, not respiration.