Answer: C. Muslims
Explanation:
After the death of The Prophet, Muslims spread out of Arabia and began to conquer territory under the his successors. Eventually the Umayyad Caliphate captured a lot of territory in the Middle East from the Byzantine empire which was a Christian empire.
In response, Pope Urban II declared the Crusades in an effort to save the Byzantine Empire against the Muslims and also to retrieve the Holy Land of Israel and Jerusalem from the Muslims.
