Answer:
b) Greece city-states were weakened by war and unable to form a new alliance
Explanation:
Phillip II of Macedon was the king that managed to make the Macedonian Kingdom into a force to be reckoned with. He rebuild and modernized the army, as well as strengthening the economy. The Greek city-states, despite being weakened from the conflicts, didn't really saw the real danger that Macedonia might pose to them, and that backfired on them. Once Phillip managed to take over Paionia and establish nice relations with the Paionians after the invasion, as well as taking over parts of Thrace and Illiria, the sights were set on the Greek city-states. With strong, modernized, well organized army, strengthened even more by the presence of the strong Paionian cavalry, Phillip moved in Greek territory, managing to easily defeat the city-states and take over them, apart from Sparta which was left alone.