Which organ system brings oxygen to body cells and removes waste gas?

• A. The respiratory system
• B. The circulatory system
• C. The digestive system
• D. The nervous system

Answer: (A)

Gas exchange with the air happens in the lungs, where oxygen moves into the blood and carbon dioxide leaves the blood to be exhaled. This makes the respiratory system the one that supplies body cells with oxygen and removes waste gas. The circulatory system then transports the oxygenated blood to tissues and brings back deoxygenated blood, but the actual gas exchange occurs in the lungs. The digestive system handles nutrients, and the nervous system coordinates body functions, so they don’t perform this gas-exchange role.