Answer:
C. It was using indulgences for financial benefits.
Step-by-step explanation:
Martin Luther, a German theologian and key figure in the Protestant Reformation, criticized the Roman Catholic Church primarily for its practice of selling indulgences. Indulgences were certificates issued by the church, which were believed to reduce the punishment for sins and provide a shortcut to salvation or the release of souls from purgatory.
Luther strongly objected to the sale of indulgences on the basis that it exploited the faith of believers and undermined the true teachings of Christianity. He saw this practice as a form of corruption within the church, where individuals could essentially buy forgiveness for their sins instead of truly repenting and seeking God's grace.
Luther's criticism of indulgences and his broader theological disagreements with the Roman Catholic Church led to the publication of his famous Ninety-Five Theses in 1517, which sparked widespread debate and ultimately led to the schism between Protestantism and Catholicism.