The correct statements are A and C.
A --- Athens used force to keep city-states from withdrawing from the league: Athens chose Pericles as its leader. Pericles began his government by ending a policy of conquest. He made Athens the first and most important Greek city and achieved a total hegemony over the other cities of the Delian League, which were transformed from allied cities into subjugated cities. It was the beginning of an Empire submitted to Athens, who was the one who directed the army, the navy and diplomacy and who also wanted to establish their own political regime in the cities. In 454 BC, frightened by the failure of the expedition sent to Egypt, it was ordered to move the treasure of the League to the city of Athens, where it would be safer. All these facts, together with the increase in taxes required for the maintenance of the war, caused the cities of the League to revolt and begin to feel enemies of Athens, which also imposed their currency, their weight system and even the form of government.
C --- The purpose of the League was to keep Persia from conquering Greece: This organization was a maritime military alliance, created and controlled in the beginning by the Athenian statesman Aristides (who wrote the statutes and put it in motion), in 477 BC, at the end of the Greco-Persian Wars, in order to be able to defend against possible and new attacks by the Persians.
