This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Symptoms & Signs , Subject name: Psychiatry
[{'content': 'A perception experienced in the absence of an external stimulus in clear consciousness is: \nSelect and explain. \nA. Delusion, B. Hallucination, C. Illusion, D. Pseudohallucination', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Hallucination3 criteria are essential for definition of hallucination:(A) Percept-like experience in the absence of an external stimulus;(B) Percept-like experience that has the full force and impact of a real perception; and(C) Percept-like experience that is unwilled, occurs spontaneously, and cannot be readily controlled by the percipient', 'role': 'assistant'}]