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 most important cell which contributes to the severity of periodontal disease is \nSelect and explain. \nA. lymphocyte, B. neutrophil, C. mast cell, D. plasma cell', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]