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: Surgery
[{'content': 'A 30 year old patient underwent resection of mandible for the treatment of ameloblastoma. The best graft is \nSelect and explain. \nA. Free iliac crest graft, B. Free vascularized iliac crest graft, C. 6th rib., D. Allograft of the bone', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]