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
The order of caries susceptibility of primary teeth is: 
Select and explain. 
A. 2nd molar>1st molar>canine, B. 1st molar>2st molar>canine, C. Canine>1st molar>2nd molar, D. Canine>2nd molar>1st molar
A: 2nd molar>1st molar>canine
Answer: A: 2nd molar>1st molar>canine 
Explanation: Caries susceptibility of primary teeth (in descending order)
2nd molar > 1st molar > canine > lateral incisor > central incisor
Caries susceptibility of permanent teeth (in descending order)
1st molar > 2nd molar > Max. 2nd PM > Max. 1st PM & Mand. 2nd PM > Max. central & lateral incisor > Max. canine & Mand. 1st PM > Mand. Central & lateral incisor > Mand. canine
Surfaces involved in descending order (in primary teeth)
 Occlusal > molar interproximal > incisor interproximal. (Proximal surfaces were affected more in first than in second primary molars).