The main duty of a vassal was to a. run his lord’s estate. c. farm land owned by nobles. b. advise the king. d. fight to defend his lord’s land.

The correct answer is: D

:)

d. fight to defend his lord’s land.

Explanation:

The Vassals during the Middle Ages had a series of responsibilities, such as to maintain the manor of their feudal lord, watch over the daily activities in the manor, they recruited men for the Lord's army, protected and managed his lord’s manor, supervise the serfs and peasants.

the process is called revolution because it was a process of great economic-social transformations that began in england in the xviii century.

the industrial mode of production spread throughout much of the northern hemisphere throughout the xix and early xx centuries.

the effect of this revolution was the distance between the countries, with respect to economic and political power.   after all, not all industrialized at the same time, remaining in the condition of suppliers of raw materials and agricultural products to the industrialized countries.

these differences mark to this day the nations of the world that are divided between developed and developing countries. one way to measure whether a country is advanced is to assess how industrialized it is.