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': 'Lance field grouping of streptococci is done by using : \nSelect and explain. \nA. M protein, B. Group C peptidoglycan cell wall, C. Group C carbohydrate antigen, D. M antigen', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Lancefield classification\nClassification of β hemolytic streptococci into Group A to V (except I, J) on the basis of group specific C carbohydrate.\nGriffith classification\nSerological typing of Group A Streptococcus pyogenes on the basis of M proteins into types 1, 2, 3 etc.\nGroup C Carohydrate\n\nPresent in middle layer of cell wall.\nThis antigen is an integral part of cell wall.\nSerological grouping of streptococci depend on C carbohydrate for which it has to be extracted from cell wall.', 'role': 'assistant'}]