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: Anatomy
Most common cause of AVN of the hip is - 
Select and explain. 
A. Idiopathic, B. Alcoholism, C. Caissons disease, D. Fracture neck of femur
A: Idiopathic
Answer: A: Idiopathic 
Explanation: *Most common cause of AVN of femoral head is idiopathic. Ref: Apley's 9th/e p.103