The correct answer is B) develop complex societies.
Agriculture and specialization made it possible for humans to develop complex societies.
After many years of being hunter-gatherers, humans started to settled in one place when they learned how to grow crops during the Neolithic Revolution or Agriculture Revolution. Those first civilizations developed in parts of the Middle East, the Indus Valley and Egypt. For instance, the Sumerians settled in the middle of the Tigris and Euphrates Rivers for the many advantages it had to be next to the river. The same happened with the Egyptians that settled next to the Nile River.
