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
All of the following are contraindications for root
planning EXCEPT 
Select and explain. 
A. deficient or overhanging margins of amalgam restorations, B. erosion and /or abrasion, C. recession, D. root caries
C: recession
Answer: C: recession 
Explanation: None