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: Anatomy
Parotid duct opens opposite to: 
Select and explain. 
A. Upper 1st molar, B. Upper 2nd molar, C. Upper 2nd premolar, D. Upper 1st premolar
B: Upper 2nd molar
Answer: B: Upper 2nd molar 
Explanation: Ans. B: Upper 2nd molar