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': 'False but firm belief about something which is not a fact: WB 10; MP 11 \nSelect and explain. \nA. Illusion, B. Delusion, C. Hallucination, D. Obsession', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Delusion', 'role': 'assistant'}]