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': 'The failure of a calcium hydroxide pulpotomy done on a\nprimary 1st molar is due to: \nSelect and explain. \nA. Internal resorption, B. External resorption, C. Pulp calcification, D. Pulp fibrosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]