Naturally acquired active immunity occurs when

• A. When your body makes antibodies
• B. Antibodies are from mother to fetus
• C. Vaccination and your body makes antibodies
• D. Injecting someone with antibiotics

Answer: (A)

Naturally acquired active immunity occurs when your body encounters a pathogen and actively produces its own antibodies and memory cells. This happens during a real infection, so you gain lasting protection because the immune system “remembers” how to fight that pathogen in the future. The antibodies from mother to fetus are naturally acquired but passively transferred, not actively produced by your own immune system. Vaccination also builds immunity, but it’s artificial because it uses a designed antigen rather than a natural infection. Injecting antibiotics does not create lasting immunity.