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
Microsbrasion technique of stain removal was given by: 
Select and explain. 
A. Kroll., B. McInnis., C. Nutting., D. Stewart.
A: Kroll.
Answer: A: Kroll. 
Explanation: KROLL → “MICROABRASION technique“18%  HCl. 
Indication of microabrasion: 
Fluorosis stains/any stains–limited to depth, not more than 0.2 to 0.3 mm.