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': "Which one of the following tooth brushing techniques is\nmost likely to clean the gingival sulcus? \nSelect and explain. \nA. Bass method, B. Charter's method, C. Modified stillman's method, D. Rolling stroke method", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]