The choices can be found elsewhere and as follows:
1 a pesticide 2 an antibiotic 3 a vaccine 4 a toxin
The correct answer is option 3. A dead or weakened pathogen used to establish immunity would most likely be found in a vaccine. <span>A </span>vaccine<span> typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins.</span>