What began the development of the two distinct European civilizations of the Western Roman Empire and the Eastern Byzantine Empire?

If the choices are:

A. Leaders of the Catholic Church had a major disagreement in the seventh century.

B. In the sixth century, trade flourished in the eastern regions but not in the west.

C. Around 400 C. E., Germanic tribes took over much of the empire's western territories.

D. In 395, the sons of Theodosius I each became emperor of part of the empire.

The correct answer is: D

There are two major causes: Germanic tribes moving into the Western roman Empire until its fall by Odacer in 476 A. D ... On the other hand, emperor Constantine I had chosen Byzantium, and ancient greek site, as the "New Rome", which would become Constantinople. Constantine I established Christianity as the official religion for the empire. The eastern half of the roman empire survived more than 1000 years, because of strategic location as a trading center and connection between Europe and Asia.