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.