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: Unknown
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. No resistance to penicillin has been reported
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 production of capsule of hyaluronic acid not due to M-protein. Growth characteristic of strep. Pyogenes:
On blood agar virulent stains form matt or mucoid colones while avirulent from glossy colonies.
M, T, R are proteins found on outer part of cell wall and forms the basis of Griffith classification.
M protein – acts as virulence factor and antibody against it are protective.
T and R protein – No relation to virulence