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
Most symmetric posterior tooth is 
Select and explain. 
A. Upper 1st molar, B. Lower 1st molar, C. Upper 2nd molar, D. Lower 2nd molar
D: Lower 2nd molar
Answer: D: Lower 2nd molar 
Explanation: None