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

option C) cowpox and smallpox are caused by the same virus

Explanation:

Cowpox is a skin disease that affects cattle. It is caused by an Orthopoxvirus, with lesions occurring principally on the udder and teats of the animals.

Human infection may occur from touching infected cows, and thus giving immunity to smallpox (an acute infection caused by the same poxyvirus, in HUMANS)

So, Jenner's successful use was because cowpox and smallpox are caused by the same virus

b is the answer and if you need further with anything message me