Which Problem Undermined Constantine's Hope That Adopting Christianity as Rome's

Which problem undermined Constantine's hope that adopting Christianity as Rome's state religion would bring Christian unity?

A) Donatist and Arian heresies threatened unity.
B) Ascetics fleeing civilization weakened the population.
C) Many Christians converted to Islam after the 600s.
D) Roman popes refused to accept Constantine's leadership.
E) Christian leaders made no attempt to define orthodoxy,splintering the community.