Answer: the correct answer is common political system
Explanation: Ancient Greece wasn't a single country or empire united under a single government, it was composed up of a bunch of city-states. At the center of each city-state was a strong city. The city managed the lands and area around it. Sometimes it also ruled minor less-powerful cities. The Greek name for a city-state was "polis".
Each city-state, or polis, had its own government. Some city states were monarchies ruled by kings or tyrants. Others were oligarchies ruled by a few powerful men on councils. The city of Athens invented the government of democracy and was ruled by the people for many years.
The two strongest and well known city-states were Athens and Sparta, but there were other important and influential city-states in the history of Ancient Greece.