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': 'In index of treatment needs (IOTN), treatment grade 4 indicates \nSelect and explain. \nA. Extreme / need treatment, B. Moderate / borderline need, C. Severe / need treatment, D. No need for treatment', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]