Natural Active Immunity from Pathogen Exposure

Steps:

• Define natural active immunity as the body's own antibody production after natural pathogen encounter.
• Identify options involving natural exposure versus artificial or passive transfer.
• Match exposure to live pathogen without intervention to active response.
• Eliminate passive immunity methods where antibodies are directly received.

Why B is correct:

• Inhaling the chicken pox virus exposes the body naturally to the pathogen, triggering its own active antibody production, per the definition of natural active immunity.

Why the others are wrong:

• A: Feeding on colostrum provides pre-formed maternal antibodies, which is natural passive immunity.
• C: Injection with antibodies delivers ready-made antibodies artificially, making it artificial passive immunity.
• D: Transfer through the placenta supplies maternal antibodies to the fetus, classifying as natural passive immunity.

Final answer: B