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
Precarving burnishing is helpful except 
Select and explain. 
A. Premalgam removal, B. To remove more marginal mercury, C. To remove old amalgam restoration, D. For condensation of marginal mercury
C: To remove old amalgam restoration
Answer: C: To remove old amalgam restoration 
Explanation: None