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
Variation of the eruption of the secondary dentition can be: 
Select and explain. 
A. 5-8months., B. 4-5months., C. 12-18months., D. 8-9months
C: 12-18months.
Answer: C: 12-18months. 
Explanation: Variation of eruption for primary dentition is 4-5 months.
For secondary dentition is12-18 months.