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: Pathology
[{'content': 'The most common malignant tumor of the gingiva is: \nSelect and explain. \nA. Malignant melanoma, B. Sarcoma, C. Fibro-sarcoma, D. Squamous cell carcinoma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]