The problems with succession to the role of emperor in the three major empires was caused…

The problems with succession to the role of emperor in the three major empires was caused partly by which of the following?
Multiple Choice
a. the refusal of most emperors to designate an heir or to grant the status to a firstborn male
b. the practice among all three empires of granting provinces for the emperor’s sons to administer, which exacerbated rivalries
c. the emperor’s possession of large harems that encouraged competition among wives and concubines and children
d. the Islamic practice of granting emperorship to the most accomplished general on the battlefield
e. the practice of granting command of different armies to the emperor’s different sons, which encouraged civil wars