This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Forensic Medicine
[{'content': 'A mentally ill person smells unpleasant odor when none is present. This is an example of: COMEDK 07; KCET 13 \nSelect and explain. \nA. Illusion, B. Delusion, C. Obsession, D. Hallucination', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Hallucination', 'role': 'assistant'}]