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
[{'content': 'With regard to sodium nitrite in CN toxicity: \nSelect and explain. \nA. Causes MetHb, B. Used to create more hydrocobalamin, C. Used to displace CN from Hb, D. Creates more sulfhydryl groups', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]