Active immunity results when?

• A. Exposure to a disease organism triggers the immune system to produce antibodies; long lasting
• B. The body rejects the disease
• C. Antibodies are introduced by injection
• D. Immunity is inherited

Answer: (A)

Active immunity results from exposure to a pathogen triggering the body's own immune system to produce antibodies, and it creates memory cells that provide long-lasting protection. This means the body learns to recognize and respond more quickly if the same pathogen invades again, which is why vaccines work—by training the immune system without causing disease. In contrast, antibodies can be given directly by injection to provide immediate but temporary protection (passive immunity), and the idea that immunity is inherited refers to genetic factors rather than an immune response developed after exposure. Simply having the body reject a disease doesn’t explain how lasting, specific protection is built through the body's own production and memory.