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': 'Ideal root canal filling for primary teeth \nSelect and explain. \nA. Calcium hydroxide-iodine mixture, B. Zinc oxide-eugenol, C. Gutta percha, D. Ferric sulphate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]