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': 'Microsbrasion technique of stain removal was given by: \nSelect and explain. \nA. Kroll., B. McInnis., C. Nutting., D. Stewart.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: KROLL → “MICROABRASION technique“18%\xa0 HCl.\xa0\nIndication of microabrasion:\xa0\nFluorosis stains/any stains–limited to depth, not more than 0.2 to 0.3 mm.', 'role': 'assistant'}]