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