Which factor directly influenced the different types of government that formed in Greece and Persia during the classical era?

A. The Persian Empire was warlike, while the Greek city-states rarely fought against their neighbors.
B. The people of Persia were much wealthier and better educated than the Greeks.
C. The mountains and islands of Greece led to city-states that were more isolated than Persian cities.
D. The Greek city-state system created a need for a stronger central government than the Persian imperial system.