It Is Difficult to Date the Beginning of Byzantine History

It is difficult to date the beginning of Byzantine history with precision because:

A) Constantine never administered the Roman Empire from Constantinople.
B) Greek was the only language ever used by Roman emperors in Constantinople.
C) the Byzantine empire was the uninterrupted successor of the Roman Empire.
D) Justinian resisted new forms of thought and art throughout his life.
E) it began during the so-called Dark Ages during which very few records were kept.