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
Root completion in primary teeth is by the age of 
Select and explain. 
A. 1 - 3years, B. 5 -6 years, C. 3 - 4 years, D. 7 -8 years
C: 3 - 4 years
Answer: C: 3 - 4 years 
Explanation: None