Which body system transports lymph and supports immune defense?

• A. Circulatory system
• B. Respiratory system
• C. Lymphatic system
• D. Nervous system

Answer: (C)

The essential idea is that lymphatic transport and immune defense are functions of the lymphatic system. This system collects excess fluid that leaks from capillaries, forming lymph, and moves it through a network of lymphatic vessels back into the bloodstream. Along the way, lymph is filtered through lymph nodes and other lymphoid tissues where immune cells monitor for pathogens and mount responses. This combination of fluid transport and immune surveillance is what the lymphatic system is specialized to do. The circulatory system mainly transports blood, the respiratory system handles gas exchange, and the nervous system coordinates signaling—none of which center on moving lymph or supporting immune defense in the same way.