An in depth study of Mary Shelley's Frankenstein would not be a short research paper. Ideally you would have to have a more specific research question/focus on one aspect of the novel. An in depth study is too broad.
An analysis of protagonists in Jane Austen's works once again would not be a short research paper, if it was limited to one or two of her books then yes but not all of them.
A comparison of Homers Illiad and Odyssey once again is too broad a topic and if you were to compare everything in both novels you would be looking at a rather lengthy research paper.
Moby D*ck is full of symbolism and if you could find a way to summarize effectively and succinctly the story and maybe just focus on the actual whale as the subject matter and what it represents in the book you could definitely make a good relatively short research paper out of it.
Alternatively would be an analysis of Edgar Allan Poe's narrative style in The Black Cat. The Black Cat is a short story and ideal for this type of research paper.
The options are:
The repetition of words and patterns: this is because the children need reptition to understand something and then learn it. The reptitions are commonly used in stories for children since this can help them to understand better what the story is about.
The description of how geographical features were made: the excerpt make reference to how the geographical features were created, but not based on scientific data or facts, but in leyends and oral traditions. This help the children to stimulate their imagination and captivate them trough the story.
................................................................................................................................................................................................oh and the answer is a:)