Though his neighbors were shocked and even feared his family would take on animal characteristics,
Benjamin Jesty's intentional infection of his family with cowpox in 1774 ultimately saved them all from the much more deadly smallpox virus during their later epidemics.I think that we can eliminate A B because use a possessive pronoun (its/their) before "epidemics". I do not care about which one is correct, as the entire idea of "possessive" + "epidemic" is not correct. The epidemic does not belong to anybody
E Benjamin Jesty's family's infecting with cowpox in 1774
intentionally and
ultimately saved
them all from the much more deadly smallpox virus during later epidemics
E changes the meaning. Both the adverbs refers to "saved" and the infection is no more "intentional".
What is the difference between the remaning B and C?
B Benjamin Jesty's intentional
infection of his family
with cowpox in 1774 ultimately saved them all from the much more deadly smallpox virus during later epidemics
C the intentional
infection of Benjamin Jesty's family
with cowpox in 1774 ultimately saved them all from the much more deadly smallpox virus during later epidemics
The are words moved around between B and C. Fist of all what does "with cowpox" refer to? It refers to the infection, so B is better because the position of the word "infection" is closer to its modifier.
In the preceding sentence
"Though his neighbors were shocked and even feared his family would take on animal characteristics" his refers to Benjamin Jesty, B once more is better because places the noun closer.