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': 'In DMF index, F indicates a tooth with: \nSelect and explain. \nA. Zinc oxide eugenol filling, B. Silver amalgam filling, C. Caries below an existing restoration, D. Permanent filling in a deciduous tooth', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Indicates the number of permanent teeth that have been attacked by caries, but which have been restored to keep them in a healthy condition in mouth.\xa0\nA tooth may have several fillings, but it is counted as one tooth.\xa0\nIf a tooth has a filling but shows evidence of recurrent decay, it is counted as a decayed tooth. (Option 3 is eliminated)\xa0\nTemporary restorations are considered as Decayed (Option 1 is eliminated)\nOnly permanent teeth are considered (Option 4 is eliminated).\n\nEssentials of preventive and community dentistry\n5th edition\nSoben Peter', 'role': 'assistant'}]