This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
All are true about streptococcus Except 
Select and explain. 
A. M-protein is responsible for production of mucoid colonies, B. M-protein is responsible for virulence, C. Mucoid colonies are virulent, D. Classified based on their haemolytic propeies.
A: M-protein is responsible for production of mucoid colonies
Answer: A: M-protein is responsible for production of mucoid colonies 
Explanation: Mucoid colonies are due to the production of the capsule of hyaluronic acid not due to M-protein. Growth characteristic of Strep. pyogenes: On blood agar, virulent stains form matt or mucoid colonies while avirulent from glossy colonies. M, T, R are proteins found on the outer pa of the cell wall and forms the basis of Griffith classification. M protein - acts as virulence factor and antibody against it is protective. T and R protein - No relation to virulence Ref : 208