Question

French catholic missionaries, especially the jesuits, served their most important function on the frontier as?

Answer 1

the answer would be: Explorers and geographers on the uncharted frontier
Catholic missionaries have vowed certain duties to spread the word of their God to the people that never heard it before.
This encourages them to travel to the part of the world that is separated from the origins of their religion even though they will risk their lives by doing so.