This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Growth, Development, and Behavior, Subject name: Pediatrics
Eruption of 1st molar permanent tooth occurs at the age of: 
Select and explain. 
A. 4-5 years, B. 6-7 years, C. 7-8 years, D. 8-10 years
B: 6-7 years
Answer: B: 6-7 years 
Explanation: b. 6-7 years(Ref: Nelson's 20/e p 1768-1771, Ghai 8/e p 11)Permanent dentition begins at 6 years and is completed by 12 years (except for 3rd molar).