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': 'The optimum length of screw, for fixation of plate in mandible is \nSelect and explain. \nA. 2mm, B. 3mm, C. 4mm, D. 6mm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]