"The pope is the only person whose feet are kissed by all princes. His title is unique in the world. He may depose emperors."-Pope Gregory VII (11th century)

"An emperor is subject to no one but to God and justice."-- Frederick Barbarossa, Holy Roman Emperor (12th century)

The ideas expressed in these quotations show that during the Middle Ages in Europe:

A) popes stayed out of political matters.

B) popes and secular rulers both rejected God's authority.

C) popes and secular rulers often challenged the other's authority.

D) secular rulers controlled the church.