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
Schielder principle is 
Select and explain. 
A. Minimal enlarged apical foramen, B. Shape of the canal can be changed, C. Use of 3-5 times larger than first binding file, D. Original canal curvature should be altered to make it compatible with obturating material
A: Minimal enlarged apical foramen
Answer: A: Minimal enlarged apical foramen 
Explanation: None