Which of the following methods of disease control involves the introduction of attenuated (weakened) pathogens into an animal's body to stimulate immunity?

Vaccination introduces attenuated (live but weakened) or killed pathogens, or their antigens, to stimulate the animal's immune system to produce antibodies. Chemotherapy uses drugs to treat disease, sanitation involves hygiene practices, and serotherapy involves administering pre-formed antibodies (antiserum).