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
With regard to sodium nitrite in CN toxicity: 
Select and explain. 
A. Causes MetHb, B. Used to create more hydrocobalamin, C. Used to displace CN from Hb, D. Creates more sulfhydryl groups
A: Causes MetHb
Answer: A: Causes MetHb 
Explanation: None