The correct answer to this open question is the following.
Unfortunately, you did not mention the civilizations you learned about during the semester.
However, trying to help you, we can pick one and comment on general terms so you can use it.
We are going to talk about the oldest civilization on planet earth: the Sumerians.
Historians consider that Sumeriansare older than the Harappans of the Indus Valley, the Chinese civilization, or the Ancient Egypt civilization.
The Sumerians settled in the middle of two important rivers of the Middle East: the Tigris and Euphrates, modern-day Iraq.
There, Sumerians developed modern agriculture techniques for the time and learned how to take advantage of the flooding of the rivers to grow crops in the fertile soil.
That is why they could grow, prosper., and form impressive and powerful city-states that had their own rulers.
We are talking about important city-states such as Lagash, Eridu, Nippur, Kish, Ur, and Uruk.