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 patient complaints of diarrhea, stool examination shows ova of size <100 gm, which of the following can not be the cause: 
Select and explain. 
A. Cryptosporidium, B. Opisthorchis viverni, C. Isospora, D. E. histolytica
B: Opisthorchis viverni
Answer: B: Opisthorchis viverni 
Explanation: Ans. (b) i.e. Opisthorchis Organism Size Cyst Trophozoite E. histolytica 12-15 pm 15-30 pm E. Coli 10-35 pm 20-50 pm Giardia 9-12 pm 12-15 pm B. coli 30-200 pm 30-50 pm C. Cryptosporidium parvum 4-5 pm 3-5 pm lsospora belli 25-30pm Opisthorchis: Trematode fluke resembling C. sinesis.