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': 'Normal facial index is: \nSelect and explain. \nA. 65 - 75%, B. 75 - 80%, C. 80 - 90%, D. 100%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]