Which organ acts to filter blood and is part of the immune system?

• A. Thymus
• B. Lymphatic system
• C. Spleen
• D. Tonsils

Answer: (C)

The main idea is identifying an organ that both filters the blood and supports immune defense. The spleen fits this dual role. It cleanses the blood by removing old or damaged red blood cells and platelets in the red pulp, while the white pulp houses immune cells that respond to blood-borne pathogens. This combination makes the spleen a key player in both filtration and immunity. The thymus mainly helps develop T cells but doesn’t filter blood. The lymphatic system is a broader network, not a single organ whose primary job is blood filtration. Tonsils defend against pathogens entering through the mouth and nose, not blood filtration. So the spleen is the best answer because it uniquely handles both blood filtration and immune activity.