What Factor Allowed Christianity to Become the Dominant Religion in the Course

What factor allowed Christianity to become the dominant religion in the course of the fourth century, however gradual the process?

A) The conversion of the emperors, all of whom promoted the new faith
B) Christian appropriation of many polytheistic beliefs and traditions, including belief in many gods
C) The acceptance that Christianity found among men and women of all social groups and classes
D) The division of the Roman Empire into eastern and western kingdoms, with the result that the emperors competed against each other in a race for converts