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
A pregnant lady with AIDS complaint of diarrhea; on stool examination showing acid fast positive stain in cysts. She has: 
Select and explain. 
A. Isospora belli, B. Microspora, C. Giardia, D. E. Histolytica
A: Isospora belli
Answer: A: Isospora belli 
Explanation: Isospora belli