Thanks for the question! So we’re looking for a flaw in the skeptic reasoning. That means it has to be both something that skeptic actually does, and a logical flaw of some kind. (E) says that the skeptic failed to consider the possibility that the success wasn’t a coincidence. Is this something the skeptic fails to do? Does the skeptic conclude that Debbie actually used magic, that it wasn’t a coincidence? No, they don’t. They just said it wasn’t one of the three tricks: a plant, a trick deck, or sleight of hand. It could still be coincidence. Since the skeptic may not have failed to consider this possibility, it can’t be the correct answer.
Hope this helps! Feel free to ask any other questions that you might have.