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
Most commonly used tooth numbering system in books is 
Select and explain. 
A. Universal system, B. Zigmondy and Palmar, C. FDI, D. Grid System
A: Universal system
Answer: A: Universal system 
Explanation: In clinical practice MC is Zigmondy and palmar system(Grid system).