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: Physiology
[{'content': 'The concentration of methemoglobin to cause cyanosis- \nSelect and explain. \nA. 5 gm/dl, B. 2 gm/dl, C. 1.5 gm/dl, D. 12 gm/dl', 'role': 'user'}, {'content': 'Answer: C \nExplanation: For Cyanosis to occur,\nSulfhemoglobin should be equal or more than 0.5gm/dL\nMethemoglobin should be equal or more than 1.5gm/dL\nDeoxygenated hemoglobin should be equal or more than 5gm/dL', 'role': 'assistant'}]