Leaders of the eastern and western churches both

believed they had complete power.
had power over european kings.
believed a schism was unnecessary.
allowed priests to get married.

Among the choices, only "believed they had complete power" is the feasible choice.

Leaders of the Eastern and Western Churches both believe they had complete power. 

Since both churches represent God. They believe that they too have complete power over the people who believe in God. They were held in high regard due to their religious position and beliefs.

Several different things make up a culture like, how the people worship, their form of government, geography, and trade. religion is one of the most important things to a culture, it defines peoples life. their different beliefs form into festivities and events that merge with their culture. people that practice hinduism see cows as gods, so no doubt they would celebrate cows, and these celebrations would definitely merge with their culture. those that are buddhist live life trying to reach a certain level of peace, so no doubt would they change things in their life in order to correspond with their religion.