Answer:
This took place because people moved to the urban areas in search of jobs that were avavailablealuble.
B. they had poor pay for harsh work
We know this thanks to archaeologists who excavated many places and discovered that many early civilizations gathered around large rivers where they could develop agriculture. This was seen in places such as Mesopotamia, India, China, Egypt, etc.
The answer is B. None of the other choices were a result of that war.