Final answer:
Purgatory is the Catholic process of purification for sins after death. Indulgences were sold as a means to reduce time spent in Purgatory, a practice which Martin Luther opposed in his Ninety-five Theses. The correct option is C.
Step-by-step explanation:
The process (rather than a place) in the Catholic faith where those destined for salvation are purified of the effects of their sins is known as Purgatory. During the Middle Ages and up to the Reformation, the Church offered indulgences — these were acknowledgments for donations or other charitable works, represented by a document asserting that an individual's soul would spend less time in Purgatory as a result.
The sale of indulgences sparked controversy, particularly when Martin Luther challenged the practice in his Ninety-five Theses, arguing that only God could grant forgiveness and questioning the Church's teachings regarding the treasury of merit.