What was the major cause of hardship in the muslim world during the thirteenth century?
a. byzantine christians refused to accept that most muslims did not want to convert to christianity and they persecuted them for it.
b. christians from western europe continued their crusades to win back jerusalem, enslaving thousands of muslims as they fought.
c. most islamic rulers exercised cruel methods to keep their subjects in line.
d. central asia's mongol armies invaded and conquered parts of the muslim world more than once during this time.