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
1st sign after formocresol pulpotomy failure is 
Select and explain. 
A. Internal resorption, B. Pain, C. Discoloration of tooth, D. Bleeding
A: Internal resorption
Answer: A: Internal resorption 
Explanation: None