Industrialization created well-paid jobs in cities wich attracted a lot of people that were looking for a better life to an urban center. In some situations, even immigrants would come from other countries to work in factories. Therefore, the factories attract people to cities from the rural areas and from outside the country.
Answer:
Sumer was responsible for many inventions and important contributions to inventions of both the time and today. However, Sumerian city-states often fought with each other. They went to war for glory and more territory. This power - hungry people build walls to protect from invading armies looking to loot, pillage, and grow wealthy. The walls surrounded each city - state, closing them off from the rest of Mesopotamia. This lead to isolation, and more war. The city - states were constantly in a state of unrest.
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I think it’s going to be A