Answer: B, thesis statement
Explanation: Usually, most effective introductions would have the point they want to make inside the introduction paragraph. If you were writing an essay on why dogs are better than cats, then your thesis statement in your introduction would be something along the lines "Dogs are better than cats because..." (This sentence also helps outline the main points, and is also written usually to be restated in the conclusion, but that's besides the point)
Point is, by using the hook of making the reader question whether Dr Frankenstein himself was a monster and waiting until the body to answer it, they sacrificed the thesis statement. Technically this could work in some instances, but if you're writing an essay and want full marks, chances are you'd need a thesis.