Answer:
They had a surplus of food, they divided labor and built cities.
After the development of the irrigation systems, they could grow more wheat and that meant more food for the growth of the population.
They divided labor between themselves. Who will harvest crops, who will tend to the irrigation systems, who will tend to fields. They had a lot of other workers such as carpenters or soldiers and that means that they knew how to divide labor between the population.
They started to build cities so they could work together, trade, store food, and the cities grew as more and more people came to live there.
It is an act or agency by which an effect is produced.
Answer:
the course of history
Explanation: hope this will help :)
