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: Microbiology
[{'content': "Mycobacterium tuberculosis is best demonstrated by \nSelect and explain. \nA. Gram's stain, B. H & E stain, C. Ziehl-Neelsen stain, D. PAS stain", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]