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
Incidence of extra canal in mandibular 1st molar is seen in 
Select and explain. 
A. 10%, B. 20%, C. 30%, D. 40%
C: 30%
Answer: C: 30% 
Explanation: None