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
In mixed dentition analysis, which tooth is used for classification? 
Select and explain. 
A. Primary 1st molar, B. Primary 2nd molar, C. Permanent 1st molar, D. Any of 2 or 3
C: Permanent 1st molar
Answer: C: Permanent 1st molar 
Explanation: The first permanent teeth to erupt into oral cavity is permanent first molar. 
From that phase of dentition, it is called as mixed dentition.
Once the first permanent molar erupts into occlusion, it is used for the classification of malocclusion.