This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Organic mental disorders, Subject name: Psychiatry
[{'content': 'The characteristic symptom of organic psychosis is \nSelect and explain. \nA. Hallucination, B. Depression, C. Transient delusion, D. Anxiety', 'role': 'user'}, {'content': "Answer: A \nExplanation: All varieties of visual hallucination are found in acute organic states but small animals and insects are most often hallucinated in delirium. Reference: Fish's Clinical Psychopathology, page 23.", 'role': 'assistant'}]