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
[{'content': 'Which of the following factor is mainly responsible for virulence in Streptococcus - \nSelect and explain. \nA. Carbohydrate, B. Streptokinase, C. Streptodornase, D. M protein', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]