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': 'HIV pt with malabsorption, fever, chronic diarrhea, with an acid-fast positive organism. What is the causative agent? \nSelect and explain. \nA. Giardia, B. Microsporidia, C. Isospora, D. E. histolytica', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]