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
Microabrasion techniques for elimination of discoloration of teeth work by: 
Select and explain. 
A. Removing surface enamel, B. Bleaching stains, C. Bleaching developmental defects, D. All of the above
A: Removing surface enamel
Answer: A: Removing surface enamel 
Explanation: Surface discolorations because of fluorosis can also be removed by microabrasion, if the discoloration is within 0.2 to 0.3 mm removal depth limit.
In 1984, McCloskey reported the use of 18% HCI swabbed on teeth for the removal of superficial fluorosis stains. 
Subsequently, in 1986, Croll modified the technique to include the use of pumice with the HCl to form a paste applied with a tongue blade.