Final answer:
The correct revision using parallel structure is: 'Selena could not decide which was the cleverest: the skeleton bride holding flowers, the skeleton cowboy holding a lariat, or the skeleton poet holding a book.' This structure repeats the gerund 'holding' for each item in the series.
Step-by-step explanation:
To revise the sentence for correct use of parallel structure, you want to ensure that each part of the list is grammatically consistent with the others. The correct revision of the sentence is: Selena could not decide which was the cleverest: the skeleton bride holding flowers, the skeleton cowboy holding a lariat, or the skeleton poet holding a book. This sentence uses parallel structure by repeating the gerund 'holding' for each skeleton, thus providing symmetry and balance within the list.
Parallel structure improves readability and aesthetics, making sentences more effective and easier to follow. It also ensures the equivalence of each item in a series, which is particularly important when listing actions or descriptions that are meant to be compared, as is the case in the original sentence presented by the student.