This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
[{'content': 'Regression of milestones is seen in all except \nSelect and explain. \nA. Childhood disintegrative disorder, B. Retts syndrome, C. Landau kleffner syndrome, D. Klein levin syndrome', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Regression refers to loss of learned brain functions and is a symptom characteristic choice 1,2,3', 'role': 'assistant'}]