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\tmost\timportant\tmorphologic\tor\thistological\nconsideration in cavity preparation in primary teeth is\nthe: \nSelect and explain. \nA. Size of primary molars, B. Thickness of enamel and dentin, C. Direction of the roots below the cemento enamel junction, D. Direction of the enamel rods at the cervical region', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]