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': 'Proximal walls in a class I tooth preparation for amalgam should \nSelect and explain. \nA. Converge occlusally, B. Diverge occlusally, C. Remain straight, D. Rounded', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]