This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
[{'content': 'CMV retinitis in HIV occurs when teh CD4 counts falls below - \nSelect and explain. \nA. 50, B. 100, C. 200, D. 150', 'role': 'user'}, {'content': 'Answer: B \nExplanation: CD4 count<100 cells/mm3 REF:<\\p> MICROBIOLOGY ANANTHA NARAYANAN NINTH EDITION PAGE.473 case-3', 'role': 'assistant'}]