Which of the following describes a contributing factor to the division of the roman empire into eastern and western empires?
a. islam spread rapidly through the empire, leading to religious tensions and violent rebellions.
b. areas on the outskirts of the empire became too difficult for the roman government to control.
c. mongol invaders captured half of the empire and established an eastern roman khanate.
d. rome's central government had borrowed too much money from its wealthier neighbors.