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': 'According to WHO technical series published, CPITN probe is also known as: \nSelect and explain. \nA. 611, B. 617, C. 621, D. 625', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]