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: Pathology
"Hair-on-end" appearance in a skull roentgenogram is
seen in : 
Select and explain. 
A. Fibrous dysplasia, B. Thalassemia, C. Garre's Osteomyelitis, D. Pagets disease
B: Thalassemia
Answer: B: Thalassemia 
Explanation: None