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
Protapers of same tip diameter are 
Select and explain. 
A. Sx-S1, B. S1-S2, C. S2-F1, D. Sx-S2
C: S2-F1
Answer: C: S2-F1 
Explanation: PROTAPER INSTRUMERNTS

A unique feature of Pro Taper instructions is each one has changing percentage tapers over the length of the cutting blades.
Pro taper instruments have convex, triangular cross – sections, a changing helical angle and push over their cutting blades and a non-cutting, modified guiding tip.
The Pro Taper system is comprised of three Shaping and three Finishing instruments.