Which statement best describes the lymphatic system's overall role?

• A. It maintains fluid balance and participates in immune defense.
• B. It transports bile from the liver.
• C. It regulates body temperature.
• D. It carries carbon dioxide in the blood.

Answer: (A)

The main idea here is that the lymphatic system both maintains fluid balance in the body and actively participates in immune defense. It collects excess interstitial fluid from tissues and returns it to the bloodstream, preventing edema, and it transports immune cells and filters pathogens through lymph nodes, the spleen, and other lymphoid tissues. This dual role—fluid return and immune surveillance—captures how the system supports tissue health and protects against infection.

This isn’t about transporting bile, which is a function of the liver and biliary system, nor about regulating body temperature, which involves the hypothalamus, skin, and metabolic rate, or about carrying carbon dioxide in the blood, which is a job of the circulatory system with red blood cells and bicarbonate. So describing the lymphatic system as maintaining fluid balance and participating in immune defense best reflects its overall role.