Answer:
B. Disagreements about the use of unleavened bread and the power of the pope
Step-by-step explanation:
The Great Schism took place in 1053, but the causes and disputes were older than a century.
The most important was the Bishop of Rome's claim of preeminence as the Pope. The Eastern Christians did not agree with that claim.
The Pope tried to force Greek Churches (Eastern or Orthodox Christians) to close or adapt to Latin practices. This caused a reaction from the Patriarch of Constantinople and the subsequent Schism.