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': "Parents should begin cleaning a child's mouth \nSelect and explain. \nA. By the time first tooth erupts, B. When all deciduous teeth erupt, C. When all anterior teeth have erupt, D. When incisors and first molars have erupt", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]