Answer: Flashback
Explanation: A flashback would interrupt the current time line to take a look back at a certain point in the history of the story. This allows the reader to understand a situation in the present part of the story by giving the reader insight on past events. This elongates the story by adding unnecessary information. The information may be helpful but for a short story a flashback would not help. The story should just move on and explain events as they happen and not switch through different periods of time; past, present, future.