Answer:
A.
Step-by-step explanation:
as stated in FLVS world history:
Constantine is probably best known as the first Roman emperor to convert to Christianity. In 313 CE, he issued the Edict of Milan, which made Christianity legal in the Roman Empire. By the time of his death, it was the preferred religion of the Romans. Constantine moved the capital of the Roman Empire from Rome to Constantinople, an eastern city named after him.