Why Did the Crusaders' Goal of Keeping the Holy Land

Why did the crusaders' goal of keeping the Holy Land under Christian rule ultimately fail?

A) The Ottoman Turks proved to be too strong and resourceful of an opponent.
B) The Europeans were not willing to commit the resources necessary to maintain the crusader states when more pressing needs arose at home.
C) Muslims throughout the Middle East were able to put aside their internal differences and form a united front against the Christian threat.
D) An outbreak of bubonic plague from 1347 to 1352 put an end to any future crusades.