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. Thalassaemia, B. Sickle cell anemia, C. Hemoc hromatosis, D. Megaloblastic anemia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Thalassemia', 'role': 'assistant'}]