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: Radiology
[{'content': '"Hair on End" appearance is seen in: \nSelect and explain. \nA. Thalassemia, B. Scurvy, C. Rickets, D. Hemochromatosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Thalassemia', 'role': 'assistant'}]