The Bubonic plague was spread by * a. an overall drop in temperatures known as a “little ice age.”
B. poisoned water from the town wells.
C. the Great Famine.
D. rats infested with fleas carrying the bacterium.

D

Explanation:

A is not right, because it wasnt temps!

b is the wrong disease (that was cholera!)

the great famine is also wrong.. that was in ireland with potatoes i think?

and d is right!!! it was spread by rats in europe and asia in like the 1200's.

it increase by 12% a year from 1812-1820

napoleon the third became a empire in 1873 also known as the era of the franco-prussian war.