Answer:
C. the history of Rob and Piyush's friendship.
Step-by-step explanation:
Remember, the term flashback often refers to a sudden portrayal or recounting of an earlier moment or event in a story.
Therefore, we could recall that the flashback showcase how the friendship between Rob and Piyush was formed back in time.
The author thereby allows his readers to have an insight into the history of the friendship between Rob and Piyush.