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: Dental
[{'content': 'Average thickness of the periodontal ligament is \nSelect and explain. \nA. 0.15 to 0.38 mm, B. 0.05-015 mm, C. 0.38 -0.48 mm, D. 0.26-0.38 mm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]