Hello There!
The answer is "B"
Their warrior-kings established fortified city-states on the mainland.
Thanks to the fact that Mesopotamia was between two major rivers, Tigris and Euphrates, it was possible for agriculture to become highly developed there because the soil was extremely fertile, which led to the rise of the civilizations there.
Because the North wanted to abolish slavery and the South didn't because they were making some serious money.
Climate should be a good factor
