What was the principal cause of the Peloponnesian Wars? A. Sparta murdered Socrates.
B. A noble Athenian eloped with the wife of a Spartan king.
C. Sparta was concerned about the growing power of Athens.
D. Athens became concerned about the growing strength of the Spartan navy.

C. Sparta was concerned about the growing power of Athens.

Explanation:

The Peloponnesian Wars was an ancient Greek that was fought for about four decades starting from 431 to the 25th of April, 405 B.C.E. The war was between the two leading states; Sparta and Athens.

Sparta led the Peloponnesian League against the Athens led Delian League.

At the time, Athens was seen to experience a significant level of growth and development, thus, wielding a great amount of power and authority in the Greek world.

Hence, the principal cause of the Peloponnesian Wars was based on the fact that, Sparta was concerned about the growing power of Athens. Consequently, the Peloponnesian League led by Sparta won the war against Athens (Delian League) and this made Sparta the new leading power in Greece while Athens was badly destroyed and devastated.

a. competition with other nations.