Final answer:
One of Martin Luther's complaints about the church was the sale of indulgences.
Step-by-step explanation:
One of Martin Luther's complaints about the church was the sale of indulgences.
Indulgences were official documents issued by the Catholic Church that promised the forgiveness of sins in exchange for money. Luther believed that the sale of indulgences was a corrupt practice that misrepresented the true nature of repentance and salvation.
This issue eventually led to Luther's famous Ninety-Five Theses, which he nailed to the door of the Castle Church in Wittenberg in 1517, sparking the Protestant Reformation.
Learn more about Martin Luther's complaints about the church