The answer is B. The Great Migration was the movement of six million African Americans from the Southern U.S. to the North. As you probably know, back in the 1900's, segregation of African Americans was on the rise. At the time, the North was not involved in this segregation, so African Americans migrated to the Northern states to escape discrimination.
They gained new rights because they had contributed to the overthrow of the French. They gained prestige because they had fought alongside the new settlers of their land.
