Philip II of Macedon was able to conquer Greece because the:

A. Greeks were weakened from fighting a second front with the Persians.

B. Greek city-states had been fighting each other.

C. Persian emperor backed him with his treasury.

D. Spartans joined with him against the Athenians

B. Greek city-states had been fighting each other.

Explanation:

He was king of Macedonia from 359 BCE, although he did not dispossess his nephew Amintas IV, legitimate king, until 355 BCE, until his death. He was the father of Alexander the Great. His expansionist ideas of Macedonia and his military capacity soon led him to achieve great success. He immediately settled the power of the Macedonian monarchy both inside and outside its borders. Then he took advantage of the Social War (or War of the Allies) from 357-355 BCE to expand. It was a conflict among the Greek city-states, that resulted from the rebellion of many Greek cities against the power of Athens. In 357 BCE, Philip took the Athenian colony of Amphipolis, which controlled the gold mines of Mount Pangeo, retaining it despite promises to return it to the Athenians. Finally, Philip conquered all the Greek states and established his hegemony over Greece, constituting the Corinthian League in 337 BCE, which included all the Greek states, except Sparta.

c i believe would be the answer