Final answer:
The flashback is important because it explains the meaning of the lullaby Stanley's father sings.
Step-by-step explanation:
The flashback in the story is important because it provides the reader with a better understanding of the lullaby Stanley's father sings. In the flashback, Stanley's father explains the meaning and significance behind the lullaby, giving it a deeper emotional connection. This helps the reader to understand the bond between Stanley and his father, and how it impacts his life.