C. Her , her desire to share every detail of her life, and her endless gossip were often annoying.
Explanation:
A backstory is an introduction of events that lead up to the main story. In this story titled, "Echo and Narcissus," we are first introduced to the character known as Echo. Echo's character of being a talkative was a backstory that prepared the reader for her encounter with Narcissus.
Her talkative nature led to her punishment by the goddess Juno, thus causing her inability to communicate properly with her love interest Narcissus.
