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
The most common malignant tumor of the gingiva is: 
Select and explain. 
A. Malignant melanoma, B. Sarcoma, C. Fibro-sarcoma, D. Squamous cell carcinoma
D: Squamous cell carcinoma
Answer: D: Squamous cell carcinoma 
Explanation: None