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: Surgery
[{'content': 'Lancefield group of streptococci belongs to: \nSelect and explain. \nA. M-protein, B. Carbohydrate (C) antigen on cell- wall, C. Bile solubility, D. Sugar fermentation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Carbohydrate (C) antigen on cell- wall (Ref: Ananthnarayan-6thEd/Pg 188) "Hemolytic streptococci were classified by Lancefield serologically into groups based on the nature of Carbohydrate antigen on the cell wall." There are 20 groups, A to V, identified (without I & J). * The great majority of hemolytic streptococci that produce human infections belong to group A * Hemolytic streptococci of group A are called as Streptococcus. Pyogen', 'role': 'assistant'}]