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
Lancefield group of streptococci is based on 
Select and explain. 
A. M proteins, B. Carbohydrate ( C ) antigen on the cell wall, C. Bile solubility, D. Sugar fermentation
B: Carbohydrate ( C ) antigen on the cell wall
Answer: B: Carbohydrate ( C ) antigen on the cell wall 
Explanation: Carbohydrate contained in the cell wall of many streptococci forms the basis of serologic grouping into Lancefield groups A-H and K-U. The serologic specificity of the group-specific carbohydrate is determined by an amino sugar.Jawetz 23e pg: 213