Question

why did greek city - states form the delian league?
o to protect each other against persian attacks
o to promote trade among the city - states
o to improve the training of greek armies and navies
o to recognize athens as the leading city - state of greece

Explanation:

The Delian League was established after the Greco - Persian Wars. Greek city - states formed it mainly to have a united defense against potential future Persian attacks. Trade promotion, military training improvement, and recognizing Athens' leadership were not the primary reasons for its formation.

Answer:

to protect each other against Persian attacks