Immunology

Step 1: Define Active and Passive Immunity. Step 1:

Active Immunity: The body's own immune system produces antibodies in response to an antigen (a foreign substance like a pathogen or vaccine). It is long-lasting but takes time to develop.
Passive Immunity: A person is given pre-made antibodies from another source, rather than producing them themselves. It provides immediate but temporary protection.
Step 2: Classify the options.
Step 2:

(A) After clinical infection: The body is exposed to the pathogen (antigen) and produces its own antibodies. This is Natural Active Immunity.
(B) After administration of an antibody-containing preparation: The person receives pre-made antibodies (e.g., immunoglobulin). The body does not produce its own. This is Artificial Passive Immunity.
(C) After subclinical infection: Same as clinical infection, the body is exposed to the antigen and produces antibodies, just without showing symptoms. This is Natural Active Immunity.
(D) After immunization with a vaccine/toxoid: The body is exposed to a harmless form of the antigen and produces its own antibodies. This is Artificial Active Immunity.
Step 3: Identify the method that does not lead to active immunity.
Step 3: The administration of an antibody-containing preparation provides passive immunity, not active immunity.