Answer:
А)
Sparta's fear and jealousy of the power and wealth of Athens
Explanation:
The fundamental cause of the Peloponnesian War was Sparta's fear and jealousy of the power and wealth of Athens. When Athens created an alliance with Corcyra in 433, and started to besiege Potidaea, it threatened the position of Corinth. Sparta also feared that Athens was becoming too powerful but tried to prevent war.