Answer: A
Explanation: The Peloponnesian War lasted for almost 27 years. Even through the war ended with the 421 Truce, the Spartans won. During the war farmers and citizens who lived outside the city of Athens flocked inside for protection from the Spartans. The city had not prepared for this type of overcrowding which caused shortage of food and clean water. There was also a lack of cleanliness. Athens was unable to get rid of all the waste that the mass of people was creating. This created dieases. A unknown plague hit the city killing many Athenians which weakens their popultation and this allowed Spartans to win.