Answer: C. Active immunity
Active immunity is the body’s continuing immune response and defense against previous pathogens. This means that it requires exposure to a pathogen or antigen as like in an immunization where an artificial active immunity is building up a resistance to a disease by clonal selection and expansion builds up sufficient antibody.
Furthermore, first exposure to pathogen will lead to what is called a primary response while secondary response is if a person is exposed to the pathogen again, the response is much faster and stronger. Active immunity can endure for years or the entire life of a person.
