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
A farmer presents with pustules showing gram positive cocci, beta hemolysis, catalase negative. To show it is group A streptococci, which of the following test is done - 
Select and explain. 
A. Bacitracin, B. Optochin, C. Novobiocin, D. Bile solubility
A: Bacitracin
Answer: A: Bacitracin 
Explanation: None