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
The percentage of upper and lower first molars, where furcation entrance diameter is narrower than the width of conventional periodontal curette is 
Select and explain. 
A. 28%, B. 58%, C. 82%, D. 85%
B: 58%
Answer: B: 58% 
Explanation: None