Which of the following was a primary cause of the Peloponnesian War?

While Spartan military actions contributed to the conflict, they were largely reactive to Athenian expansionism. The initial causes of the war stemmed from Athenian policies that antagonized Sparta and its allies rather than outright aggression from Sparta itself. Therefore, Spartan actions were more a consequence than a primary cause of the war.

Athenian democracy, while significant in shaping political life in Athens, was not a direct cause of the Peloponnesian War. Many Greek city-states had their forms of governance and were more concerned with Athenian imperialism and its implications for their own sovereignty. The democratic structure of Athens did not inherently provoke conflict; rather, it was the imperialist ambitions that did.

Although the Persian Wars had a lasting impact on Greek politics, fears of Persian reprisals were not a primary cause of the Peloponnesian War. By this time, the Persian threat had diminished significantly, and the war arose primarily from internal Greek rivalries, particularly the conflict between Athenian and Spartan interests.