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 retention for class 5 restoration are placed: \nSelect and explain. \nA. In mesial and distal areas, B. Occlusal and gingival area, C. In all except the axial wall, D. At expense of axial wall', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]