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 most likely cause for the discoloration in this patient would be \nSelect and explain. \nA. Pulp necrosis, B. Dental resorption, C. Internal resorption, D. Microleakage', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]