It is A.
The West and East shared the same laws and the Eastern Roman Empire continued using these laws.
Obviously, the Eastern Roman Empire did not originate in the Western Roman Empire, they are two separate entities.
The Eastern Roman Empire was predominantly Greek and as such, the people spoke Greek. The government also got rid of Latin as its administrative language, making the Church the last organization to use it as its primary language.
In the Western Roman Empire, the Emperor was the final authority on all matters of the Roman religion. However, the Catholic Church had the Pope, which was the final authority on Christianity. In the East, the Emperor was the final authority in Christianity. They inevitably clashed on the issue of whom was more powerful than whom and it led to East-West Schism which created the Orthodox Christian church which Greece, Russia, and a few other countries followed. (Not Mine)
