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': 'A twenty year old female patient comes to the clinic with discoloration of the upper right central incisor. This tooth was intact and otherwise asymptomatic.\n\nThe common sequel following bleaching non vital teeth are: \nSelect and explain. \nA. Ankylosis, B. Periodontal pathology, C. External cervical resorption, D. Reinfection', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]