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: Pathology
[{'content': "Amyloid is stained with: September 2009, March 2013 \nSelect and explain. \nA. Lugol's iodine, B. Methyl violet, C. Congo red, D. Sudan black", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Congo red', 'role': 'assistant'}]