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
Lancefield classification of beta hemolytic streptococci is based on ? 
Select and explain. 
A. Protein percent, B. Cell wall carbohydrate antigen, C. Cell membrane M protein, D. Hemolytic propeies
B: Cell wall carbohydrate antigen
Answer: B: Cell wall carbohydrate antigen 
Explanation: Ans. is 'b' i.e., Cell wall carbohydrate antigen