Identifying Flashback in Narrative

Flashbacks are a powerful literary device that allows authors to provide context and background information about characters or events that have significantly influenced the narrative. In the following excerpt, identify the sentence that effectively employs a flashback to enhance the reader's understanding of the protagonist's current situation:

As she stood at the edge of the river, her thoughts drifted back to the summer of her youth, a time when the world was full of possibilities. On those long, sun-soaked days, she remembers laughing with her brother, splashing in the water, and dreaming of a future untainted by fear. It was only years later that she understood the fragility of happiness, a lesson learned far too late.