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
Streptolysin O is inactivated by 
Select and explain. 
A. CO2, B. Nitrogen, C. Oxygen, D. Serum
C: Oxygen
Answer: C: Oxygen 
Explanation: Streptococci produce 2 types of Streptolysin ( O&S) based on oxygen dependency. Streptolysin O is oxygen labile. It is inactive in the presence of Oxygen. Streptolysin O is antigenic and ASO titre is a standard serological diagnosis of Acute Rheumatic fever. Streptolysin O & S both can cause hemolysis.