Final answer:
During the Middle Ages, 90% of the population who lived on manors were serfs, who were peasants subject to noble overlords and owed them rents and services.
Step-by-step explanation:
In the context of European society during the Middle Ages, 90% of the population who lived on manors were serfs. These serfs were peasants who were subject to noble overlords and owed them rents and other services in a system known as manorialism. They lived in villages and worked on the lord's land, sharing farm implements and cooperating in agricultural tasks.