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: Microbiology
Which of the following factor is mainly responsible for virulence in Streptococcus - 
Select and explain. 
A. Carbohydrate, B. Streptokinase, C. Streptodornase, D. M protein
D: M protein
Answer: D: M protein 
Explanation: None