The correct option is D Attenuated pathogens
Polio drops that are administered into the body contain attenuated pathogens. Attenuated vaccines are the type of vaccines which are created by reducing the virulence of a pathogen, but still keeping it viable.
Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response. Just 1 or 2 doses of most live vaccines can give you a lifetime of protection against a germ and the disease it causes.