Concept:Feudalism was an economic and social system built on land ownership and farming.
Explanation:In a feudal system, the lord owned large landed estates.
The lord granted portions of land to vassals or serfs.
In return, these tenants farmed the land and gave the lord part of their harvest, labour, and military support.
Since land was the main source of wealth, income, and power, agriculture was the central economic activity.
Trade and capital were less important in this system.
Slavery existed in some places but was not the defining economic foundation of feudalism.
Answer:A. agriculture