This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2017, Subject name: Microbiology
A HIV positive individual having diarrheal episodes stool examination reveals on oocyst of size 8-10 Micron, what could be the diagnosis? 
Select and explain. 
A. Cyclospora, B. Cryptococcus, C. Cryptosporidium parvum, D. Isospora
A: Cyclospora
Answer: A: Cyclospora 
Explanation: Parasites Size of oocyst Cryptosporidium parvum 4-6 micron Cyclospora 8-10 micron Isospora 23-36 micron They all are acid fast so the appear similar in colour under acid fast stain. So, size of oocyst is used to identify them.