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': 'Moderate papillary recession with slightly open incremental space is classified as: \nSelect and explain. \nA. Class 1 embrasure., B. Class 2 embrasure., C. Class3 embrasure., D. Class4 embrasure.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]