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': 'Probing depth of a pocket is assessed by: \nSelect and explain. \nA. Williams probe, B. Nabers probe, C. DNA probe, D. RNA probe', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]