Answer:
Correct answer is B. He legalized Christianity and changed the capital.
Explanation:
Option B is correct because he legalized Christianity with the Edict of Milan in 313 and also created new capital, named Constantinople after him.
A is not correct as he didn't split with Rome, he strengthen the Empire.
C is not correct as he changed the system and ruled as a sole ruler.
D is not correct as he was a part of the council of four, but decided the full authority in the country after defeating Licinius.
D.) taking a diplomatic or legislative action to force the European powers to negotiate with the United States
