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': 'Root conditioning with citric acid helps in \nSelect and explain. \nA. Removal of endotoxin, B. Removal of smear layer, C. Regeneration of bone, D. All the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]