Charlemagne forced all of the people he conquered to a. join the military b. work as slaves c. serve as missionaries d. convert to christianity

D. convert to Christianity

is the correct answer.

(d) rivers.

explanation:

civilizations developed around rivers because their waters provided places to hunt and fish. also, as the rivers flooded, the lands around them became fertile. this allowed them to support farming. this is especially true of the nile river, which flooded the same time each year.

location is the answer to this