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
[{'content': 'Parotid duct opens opposite to: \nSelect and explain. \nA. Upper 1st molar, B. Upper 2nd molar, C. Upper 2nd premolar, D. Upper 1st premolar', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: Upper 2nd molar', 'role': 'assistant'}]