Active immunity is not acquired by:
Ans. is 'c' i.e., Immunoglobulin transfer (Ref: Ananthanarayan, 9th/e, p. 82 - 83 and 8th/e, p. 86, 87)* Immunoglobulin transfer gives passive immunity.* Rest of the other options are examples of active immunity.
Infection
Vaccination
Immunoglobulin transfer
Sub - clinical infection
Immunology