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': 'Senile caries refers to: \nSelect and explain. \nA. Residual caries., B. Root caries., C. Pit and fissure caries, D. Recurrent caries.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Root caries or senile caries occur on the tooth that has been exposed to the oral environment.', 'role': 'assistant'}]