Which best describes the structure of mary shelleys frankenstein

The Gothic novel Frankenstein, or The Modern Prometheus is the result of Mary Shelley's travels to Geneva, Switzerland, with her future husband Percy Bryce Shelley, Dr. John Polidori and Lord Byron, themselves famous authors, and an entertaining contest between those friends about who could write the best horror story.
The structure of Frankenstein is very largely determined by the way in which the narrative is organised: this is fully discussed in the section Narrative. Readers are likely to be struck by the way in which each narrative is framed by another, so that different parts of the story are recounted by different narrators.