The correct option is D Pope Gregory VII
The Pope used his power to excommunicate secular kings and emperors, and free their subjects from their oaths of obedience. Losing control over subjects resulted in weakening of the power of the king. This was a major issue for the rulers of Western Europe. During the years between 1056 and 1106, Henry IV reigned as the Holy Roman Emperor. When he opposed the control of the pope over the empire, Pope Gregory VII, excommunicated him from the empire.