Answer:
City -state is a political entity that was created in ancient Mesopotamia, but also existed for example in Ancient Greece. The forms of government were different, but most of them were created on a territory of a certain city, that also included a smaller territory that surrounded that city.
Babylonia is a state created on a soil of Mesopotamia in 2nd Millennium BC. The center of the state was the city of the same name (Babylon) and there were two empires with this name - Old and New.
Mesopotamia is a region (area) between rivers Euphrates and Tigris, where one of the first civilizations emerged.
Stele is a type of monument, typical for ancient Mesopotamia, which usually included some texts (mostly religious). It is also an important historical source for the history of Ancient Mesopotamia.
