Answer: c. universalizing religious communities spreading across Asia along trade routes
Step-by-step explanation:
Although Christianity was originally persecuted in Iran, it was made legal after 451, and Nestorian Christianity had become the prevailing Christian sect in the Sassanid Empire by 491.
Christians became self-governing of their inner religious and civil law proceedings, a status similar to the one achieved by the Jews.
Nestorian Christians were in charge of most of the empire´s trade through central Asia and as far as China and India, and they adopted trade as an opportunity to develop their proselytizing efforts.