Answer:
Poetry of Homer.
Step-by-step explanation:
The poetry of Homer was a very important common trait that contributed to pulling the Greek city-states together. The poetry of Homer contributed to the creation and development of a cultural identity that unified the Greek city-states. It gave rise to common stories, myths and other cultural traits. In this way, it allowed the Greek citizens to feel like they belonged to a defined civilization, and to have a sense of connection between them and other Greek citizens.