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': 'For a class V cavity for amalgam: \nSelect and explain. \nA. Mesio-distal walls are parallel and occluso-gingival walls converging, B. Mesio-distal walls diverging, occlusogingival walls converging, C. MD walls diverging, OG walls diverging, D. MD walls and OG walls parallel', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]