Question

What brought an end to the system of serf labor?

Lords found cheaper workers for their lands.
Peasants replaced serfs in the fields.
Workers were in short supply.
Lords decided serf labor was unfair.

Answer 1

Workers were in short supply.

The Black Death and other demographic changes sharply reduced the population, giving peasants bargaining power to demand wages, leave manors, or refuse servile obligations — this labor shortage undermined the serf system.