Answer: He is amused by the story and does not take it seriously.
In this passage, the police officer seems amused to hear the story that Julie and Rebecca explain to him. He was smiling while getting into the patrol car, which means he is not concerned. Moreover, the text places "crime scene" between quotation marks. This is often done in order to show that the idea is not taken seriously.
D. he's amused he couldn't have been serious because he got serious arriving at the scene. he wont nervous or worried because he was smiling on the way there.
It tells the reader that the elves live in comfortable, lively and welcome homes. This shows that the nature of the elves is to invite and welcome guests.
