What major religion began to form during the Medieval Era?

Christianity

Explanation:

From a marginal religion to the dominance in Europe, Constantine took the first step in accepting Christians in 313, with the Edict of Milan, which instituted religious tolerance in the empire.  In 380 AD, Theodosius I officialized this religion, and over time, the church became more powerful, controlling every aspect of the European society.

answer; /// i do believe that the correct answer is (a); a farming tribe that settled primarily along the mississippi and arkansas rivers;

it was the first major victory for the colonists.