Final answer:
Reformers in the 11th century addressed clerical marriage and simony; simony is the sale of church offices. They enforced clerical celibacy and could excommunicate kings who interfered with ecclesiastical appointments.
Step-by-step explanation:
Eleventh-century church reformers focused on addressing two critical breaches of canon law: clerical marriage and simony. Simony referred to the sinful practice of buying and selling church offices, which reformers such as those from the Cluniac movement strongly condemned.
They advocated for bishops to be elected by the clergy, free from secular lordship. Additionally, the reforms targeted clerical celibacy, enforcing it to prevent church positions from becoming hereditary benefices.
These changes sparked conflicts with European rulers, with the church asserting its power by declaring that kings interfering in ecclesiastical appointments could face excommunication, a severe penalty that could destabilize a monarch's rule by casting them out of the church community and denying sacraments.