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': 'Diameter of the bristle of the soft toothbrush is: \nSelect and explain. \nA. 0.075 mm, B. 0.2 mm, C. 0.3 mm, D. 0.4 mm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]