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': 'Pulpless primary incisor (abscess caused by trauma) in 4\nyear old patient can be effectively treated by \nSelect and explain. \nA. Pulpectomy, B. Extraction, C. 5-minute formocresol pulpotomy, D. 7-day formocresol pulpotomy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]