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': 'Floor of class II cavity for amalgam restoration, occlusally should be: \nSelect and explain. \nA. In enamel, B. In dentin, C. In DEJ, D. Just above the roof of pulp chamber', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]