(d) They were extremely radical.
The lord would provide to the vassal land from which they could make money from and in return the vassal would contribute troops to the lords army. Sometimes vassals would also pay a small fee of grain or various other goods as a sort of tax for the land.
It led to the start of world war 1. Archduke Ferdinand was from the Balkans which was known as the "powder keg" of Europe during this time period.
