The correct answer is A) city-state.
When the city of Athens took over territory outside its walls, it changed from a city to a city-state, which led to the development of a complex government.
In ancient Greece times, geographical features played an important role in the formation of city-states. Mountains, many islands, the sea, were important features that divided different territories and that is why they formed city-states. Athens was the most important city-state. It was followed by Sparta, a place of fierce warriors. Other important city-states were Thebes, Corinth, Rhodes, Aegina, and Argos.