This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
All are sources of free radicals except - 
Select and explain. 
A. Fentons reaction, B. Glutathione, C. Myeloperoxidase, D. Nitric oxide
B: Glutathione
Answer: B: Glutathione 
Explanation: Harshmohan textbook of pathology 7th edition. Reduced glutathione protects RBCs against oxidant stress produced by the oxygen free radicals. MPO, Fenton reaction produce oxygen free radicals. NO is a free radical..