This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'Streptococcus is classified based on \nSelect and explain. \nA. M protein, B. Cultural characteristics, C. Bile solubility, D. Cell wall carbohydrate', 'role': 'user'}, {'content': "Answer: D \nExplanation: Hemolytic streptococci were classified by Lancefield serologically into groups based on the nature of a carbohydrate (C) antigen on the cell wall. These are known as Lancefield groups, twenty of which have been identified so far and named A-V (without I and J). Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 211", 'role': 'assistant'}]