Option C, selling indulgences, was one of Martin Luther's main criticisms of the Church. He strongly objected to the selling of indulgences, which were essentially pardons for sins that could be purchased from the Church, believing that salvation could not be bought with money. Additionally, Luther had other criticisms of the Church, including corruption among the Roman clergy and a focus on rituals and sacraments rather than personal faith in God. However, option B is the closest answer to Luther's main criticism.
