Which of the folllowing was the most troubling aspect of muhammad's death for the islamic religion?

a. he died at the ka'ba
b. he died unexpectedly
c. he died without an heir
d. he appeared to have been murdered

C. he died without a heir

I just took the quiz, it was right

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).