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 teeth the proximal aspect shows rhomboidal appearance: \nSelect and explain. \nA. Maxillary posteriors, B. Mandibular posteriors, C. Maxillary anteriors, D. Mandibular anteriors', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]