Step 1: Concept
Certain organs in the body serve as filters to maintain the quality of the blood and support immune defense.
Step 2: Meaning
This organ acts as a blood filter, removing aging erythrocytes and recycling iron.
Step 3: Analysis
The pancreas is for digestion/insulin, the heart for pumping, and the kidney for urine filtration. The spleen is the largest lymphoid organ and specifically filters the blood to remove pathogens and old RBCs.
Step 4: Conclusion
The spleen is the primary organ designated for blood filtration and RBC recycling.
Final Answer: (C)