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
Root conditioning with citric acid helps in 
Select and explain. 
A. Removal of endotoxin, B. Removal of smear layer, C. Regeneration of bone, D. All the above
D: All the above
Answer: D: All the above 
Explanation: None