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
In preparing an endodontically treated tooth for receiving a cast post, the minimal amount of gutta 
percha to be maintained for proper apical seal is 
Select and explain. 
A. 1 mm, B. 8 mm, C. 4 mm, D. 0 mm
C: 4 mm
Answer: C: 4 mm 
Explanation: None