The correct answer is option d.
A vaccine refers to a biological preparation, which offers active acquired immunity to a specific disorder. A vaccine usually comprises an agent, which signifies a disease-causing microbe and is usually made from killed forms or attenuated microbe, one of its surface proteins, or from its toxins.
The agent instigates the immune system of the body to determine the agent as a danger, destruct it, and to further destroy and identify any of the microbes related with that agent, which it may come across in the coming future.
