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
[{'content': 'Most common cause of AVN of the hip is - \nSelect and explain. \nA. Idiopathic, B. Alcoholism, C. Caissons disease, D. Fracture neck of femur', 'role': 'user'}, {'content': "Answer: A \nExplanation: *Most common cause of AVN of femoral head is idiopathic. Ref: Apley's 9th/e p.103", 'role': 'assistant'}]