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': '24 Year old AIDS pt. develops chronic abdominal pain, low grade fever, diarrhoea, malabsorption. Oocysts demonstrated in stool. Likely cause of his diarrhoea is - \nSelect and explain. \nA. E. histolytica, B. G lamblia, C. Microsporidia, D. Isospora belli', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]