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': 'Most important morphologic or histologic consideration\nin cavity preparation in primary teeth is \nSelect and explain. \nA. Size of primary molars, B. Thickness of enamel and dentin, C. Direction of roots below CEJ, D. Direction of enamel rods cervically', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]