Answer:
Correct answer is They helped one another maintain power over people.
Step-by-step explanation:
First option is not correct as the Church gained so much authority that they were even able to oppose the rulers of Holy Roman Empire.
Second option is also not correct, although it has certain amount of truth as they had frequent quarrels about their dominion of power.
Third option is therefore correct as they wanted to have the control over people, and were both involved in the feudal system.
Fourth option is also not correct as Pope didn't have this type of authority.