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': 'When pulp cannot be extirpated in narrow canals, which of the following can be used \nSelect and explain. \nA. Obtundant, B. Astringent, C. Haemostatic, D. Mummifying agent', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]