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
Classification of pathogenic streptococci into group A, B, C, D and G is based on - 
Select and explain. 
A. Color of colonies on blood agar, B. Antigenicity of cell wall carbohydrate, C. Presence or absence of capsule, D. Presence or absence of M protein
B: Antigenicity of cell wall carbohydrate
Answer: B: Antigenicity of cell wall carbohydrate 
Explanation: Ans. is 'b' i.e., Antigenicity of cell wall carbohydrate