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': "All are reversible causes of dementia except \nSelect and explain. \nA. Hypothyroidism, B. Hydrocephalus, C. Meningoencephalitis, D. Alzheimer's disease", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Alzheimer&;s is the commonest cause of dementia The diagnosis of Alzheimer&;s dementia is by an exclusion of all other causes of dementia as there is no distinct diagnostic clinical features or laboratory investigations. At present Alzheimer&;s dementia is not considered a treatable disorder (Ref: a sho textbook of psychiatry, Niraj Ahuja, 7th edition, pg no.23)', 'role': 'assistant'}]