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 is used for: 
Select and explain. 
A. Streptococci and based on protein, B. Streptococci and based on carbohydrate, C. Staphylococci and based on protein, D. Gonococci and based on protein
B: Streptococci and based on carbohydrate
Answer: B: Streptococci and based on carbohydrate 
Explanation: Streptococci and based on carbohydrate