Answer: In Medieval Europe, knights pledged loyalty to vassals, who in turn pledged theirs to powerful lords, and serfs labored in the fields.
Explanation:
A rigid hierarchy refers to one where people who are born into a certain position in life, find it quite hard to move from it or rather one where there are different social classes and people had to be classified in one class for the system to work.
The system during medieval times was much like this. Social classes existed that determined a person's worth in society such as the knights, vassals, Lords and Royals. There was also the serfs who were considered the lowest in the hierarchy.
One effect that plentiful harvests had on ancient civilizations of the mainland's river valleys was to help have larger populations and the need to have materials to survive.
Sedimentary rocks are often found in a layer formation. These rocks are were formed in water by the deposition of material at the earths surface. The correct answer is A.
