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
When it is made up of same steel, size 55, which will be more prone to fracture: 
Select and explain. 
A. Triangular reamer, B. Rhomboid cross section file, C. Square cross section file, D. Headstrom file
D: Headstrom file
Answer: D: Headstrom file 
Explanation: None