Correct option is C. Collection of heat killed disease causing bacteria and viruses
A vaccine is a biological preparation which provides active acquired immunity to a particular disease. A vaccine 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. The agent stimulates the body's immune system to recognize the agent as a threat, destroy it and keep a record of it so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.