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.
The tool that would be most useful to him would be a seismometer. It is an<span> instrument that measure motion of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions. Hope this answers the question. Have a nice day. </span>
