The lymphatic system includes lymph nodes positioned throughout the body. Lymph nodes serve as filters and remove pathogens from the blood as they pass.

• A. They produce digestive enzymes
• B. They filter pathogens from the blood as they pass
• C. They circulate oxygen in the blood
• D. They store energy as fat

Answer: (B)

Lymph nodes act as filtration stations for the immune system. As lymph flows through these nodes, specialized cells like macrophages and lymphocytes inspect it, capturing and attacking invading pathogens. This means lymph nodes help remove pathogens from the lymph as it passes through, preventing spread and triggering an immune response. That idea aligns best with the statement about filtering pathogens as the fluid moves through the system. The other functions listed aren’t roles of lymph nodes—producing digestive enzymes is a pancreatic function, circulating oxygen is the job of red blood cells and the lungs, and storing energy as fat is handled by adipose tissue. Note that lymph nodes filter lymph, not blood, though both systems work together to keep us healthy.