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
Antibiotic used to for sensitivity in identification of streptococcus pyogenes? 
Select and explain. 
A. Bacitracin, B. Novobiocin, C. Penicillin, D. Optochin
A: Bacitracin
Answer: A: Bacitracin 
Explanation: Ans. is 'a' i.e., Bacitracin Senstivity to bacitracin is employed as a convenient method for differentiating str. pyogenes from other hemolytic streptococci (Maxted's observation).