The correct answer is:
C. The Catholic Church has a single leader in the pope; the Eastern Orthodox Church has no single leader.
Explanation:
One of the main differences between the Roman Catholicism and the Eastern Orthodoxy is that the Catholic Church has a supreme authority; the Pope, he is infallible and has authority over the whole Church, and the Eastern Orthodox Church doesn't have a centralized authority, all Bishops are leaders of their Church and are not infallible like the Pope; the Patriarch of Constantinople, who is traditionally seen as first among equals doesn't have a real supremacy, it is only a courtesy title.