In the context of feudal times, who were serfs?

Serfs were primarily peasants who were bound to the land they worked on and were obligated to serve a lord in a feudal system. This relationship was a fundamental aspect of feudalism, where the lords provided protection and land in exchange for labor and a portion of the agricultural output from the serfs. Unlike free peasants, serfs could not leave the land without permission and had limited rights, making them integral to the economy of the time.

The other options describe different social classes during the feudal period. Nobles were landowners and part of the ruling class, while high-ranking military officers typically held titles of nobility and commanded armies. Members of the clergy played significant spiritual and often political roles but were distinct from the peasant class. Understanding the role of serfs in feudal society highlights the economic and social structures that defined the medieval period.