Which system serves as the transportation highway for the body, moving substances such as oxygen, carbon dioxide, and nutrients?

• A. Circulatory system
• B. Digestive system
• C. Immune system
• D. Musculoskeletal system

Answer: (A)

The circulatory system acts as the body's transportation highway, moving essential substances to and from every cell. Blood carries oxygen from the lungs to tissues, and brings carbon dioxide back to the lungs to be exhaled. It also delivers nutrients absorbed from the digestive system to cells that need them and transports wastes to organs that remove them. The heart powers this network, with arteries carrying blood away from the heart, capillaries where exchanges occur, and veins returning blood to the heart. While the digestive system processes and absorbs nutrients, the immune system defends against invaders, and the musculoskeletal system provides structure and movement, none of these serve as the body-wide transport network like the circulatory system.