What caused the Greeks to unify in defense of their culture and way of life?

Question

A. The attempt of Athens to force democracy on all the poleis
B. The attempt by Sparta to control all of Greece
C. the ivasion of Corinth by Thermopylae
D. The threat of the Persian Empire conquering Greece

Answer 1

D. The threat of the Persian Empire conquering Greece

The Greeks unified in defense of their culture and way of life primarily in response to the threat posed by the Persian Empire, particularly during the Persian Wars in the early 5th century BCE. The invasions by Persian forces, notably under King Xerxes, prompted various Greek city-states to come together in a coalition to protect their independence and way of life.