this is an OPINION based question. but i will give you MY personal opinion. but i dunno how it will help, its YOUR opinion NOT MINE.
my opinion:
i think it was a complex period, but very helpful in many ways. there are pros and cons to it, but the many changes lead to this modern day period. some things may have happened that may have lead to bad paths, but this period was greatly effective to our present days. so i think that this complicated period was helpful, and worth what happened in it.
Coal and wood are two sources which had been used extensively since the 18th century. when steel was commercialized heavily using the Bessemer Proces later at the 19th century. At this time, petroleum became the major energy source of energy and was even used extensilvely in other processes as converting petroleum to fuels.
The answer is D) Decentralized authority of many different rulers
Feudalism means there are feudal kings who have large regions. They divide their state into little pieces and give those pieces to their generals. Generals did the same thing too. They divide their piece and give them to their soldiers by rank.
A is an absolute monarchy where the monarch (king, mansa, shah) is the leader of the country and has absolute power.
B is a representative democracy which means people elect delegates to make the decisions for them.
C is a theocracy. In this system, the ruler claims to have a religious power or a religious authority.
