Physician Edward Jenner Promoted the Use of Cowpox,a Harmless Pathogen

Physician Edward Jenner promoted the use of cowpox,a harmless pathogen related to the dangerous smallpox,as a vaccination to provide patients immunity from future smallpox epidemics.This is an example of

A) passive immunity.
B) active immunity.
C) an inflammatory response that decreased the IgE production and increased T cells.
D) developing high levels of complement.
E) developing high levels of interferon although Jenner did not realize these diseases were viral.