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: Psychiatry
[{'content': 'An elderly male patient on evaluation is found to have delusions, hallucinations and disturbed cognitive function. What is he most likely suffering from? \nSelect and explain. \nA. Paranoid psychosis, B. Organic brain syndrome, C. OCD, D. Dissociative disorder', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Organic brain syndromes refers to physical disorders that cause impaired mental function. It is the most common form of mental illness in elderly. In acute form it can present with delerium and in chronic form as dementia.', 'role': 'assistant'}]