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
HIV pt with malabsorption, fever, chronic diarrhea, with an acid-fast positive organism. What is the causative agent? 
Select and explain. 
A. Giardia, B. Microsporidia, C. Isospora, D. E. histolytica
C: Isospora
Answer: C: Isospora 
Explanation: None