The correct option is C Clashes between the Athenian league and Peloponnesian league.
Under Pericles, Athens was leading a league of city-states in a military alliance known as the Athenian league. Meanwhile, the Spartans were part of the Peloponnesian League of city-states. Eventually, the scuffle between these two leagues resulted in the Peloponnesian War. It became a fifteen-year conflict between Athens and Sparta and their allies.