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': 'Lancefield classification of beta hemolytic streptococci is based on ? \nSelect and explain. \nA. Protein percent, B. Cell wall carbohydrate antigen, C. Cell membrane M protein, D. Hemolytic propeies', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Cell wall carbohydrate antigen", 'role': 'assistant'}]