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': 'The enamel of the posterior teeth is thickest at \nSelect and explain. \nA. Cervical third of buccal surface, B. Middle third of buccal surface, C. Middle third of lingual surface, D. Occlusal surface', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]