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
[{'content': 'Which Permanent tooth has most prominent transverse ridge \nSelect and explain. \nA. Lower 1stpremolar, B. Upper 1stpremolar, C. Lower 1st molar, D. Upper 2ndmolar', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]