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
"Head at risk" sign is seen in ? 
Select and explain. 
A. Pehes disease, B. Ewing's sarcoma, C. Osteomylitis, D. Paget's disease
A: Pehes disease
Answer: A: Pehes disease 
Explanation: Ans. is'a'i.e., Pehes disease (Ref: Pediatric Ohopedic Deformities p.326) "Head at risk sign is a radiological prognostic sign for Pehes disease (also k/a Legg-Calves- Pehes disease or Coxa Planaor Idiopathic avascular necrosis of femoral head).