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': '1st sign after formocresol pulpotomy failure is \nSelect and explain. \nA. Internal resorption, B. Pain, C. Discoloration of tooth, D. Bleeding', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]