contestada

Jenner's successful use of cowpox virus as a vaccine against the smallpox virus was due to the fact that ______. (A) the cowpox virus made antibodies in response to the presence of smallpox(B) the immune system responds nonspecifically to antigens(C) cowpox and smallpox are caused by the same virus(D) there are some epitopes (antigenic determinants) common to both pox viruses