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
Which of the following is the current concept of clasp design of bar clasp? 
Select and explain. 
A. I bar clasp, B. RPI system, C. RPA system, D. RPM system
B: RPI system
Answer: B: RPI system 
Explanation: The RPI is a current concept of bar clasp design, and refers to the rest, proximal plate, and I bar component parts of the clasp assembly.