Answer:
A. for Athens to gather support from other Greek city-states to push Persia out of the Aegean.
Step-by-step explanation:
The Delian League was an alliance between different Greek city-states led by Athens. This league was formed with the original purpose of liberating Greek cities from Persian rule. About 300 cities were part of this league, however, it was de facto dominated by Athens. The League was only dissolved in 404 BCE after Athens' defeat against Sparta in the Peloponnesian War.