Hello there!
The event that marked the end of the Peloponnesian War was: C) The 421 Truce.
Explanation:
The Great Peloponnesian War was an ancient war between Athens and Sparta from 431 to 405 b.C.
It started with the Spartan invasions to Attica, taking advantage of its naval power. Six years later, Athens attacked Syracuse, Sicily with all its expeditionary force and failed. The battle of Aegospotami in 405 b.C. ended the war, destroyed the Athens' fleet and ended up with its surrender one year after.
The Fifty-Year Peace, also known as the Peace of Nicias was a treaty signed between Athens and Sparta in March 421 BC, this ended the first half of the Peloponnesian War.
