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 is based on which of the following cellular structure? \nSelect and explain. \nA. M protein, B. Carbohydrate antigen, C. Cell wall peptidoglycan, D. T-protein', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lancefield classification is a serological classification of beta hemolytic streptococci. This classification is based upon the detection on group specific carbohydrate antigen on the cell wall of streptococci. Beta hemolytic streptococci are classified into 21 serologic groups known as Lancefield groups designated from A to V. Griffith typing: Based on the presence of M, T, and R protein antigens present on the cell surface, Streptococcus pyogenes are classified into 80 serotypes. M protein is the most impoant type specific antigen. Ref: Textbook Of Microbiology And Immunology By Parija, page 191-2.', 'role': 'assistant'}]