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
The purpose of a root canal sealer is to: 
Select and explain. 
A. Seal the tubules of the dentine, B. Stimulate healing in periapical region, C. Prevent discoloration, D. Fill the space between solid core material and the pulp canal walls
D: Fill the space between solid core material and the pulp canal walls
Answer: D: Fill the space between solid core material and the pulp canal walls 
Explanation: None