This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitreous and retina, Subject name: Ophthalmology
[{'content': 'The most common organism causing chorioretinitis in HIV is \nSelect and explain. \nA. CMV retinitis, B. Toxoplasma chorioretinitis, C. Syphilitic retinitis, D. Pneumocystis carini', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Refer: AK Khurana Comprehensive Ophthalmology, 6th edition, pg no. 470 - 472)Cytomegalovirus (CMV) is the most common cause of chorioretinitis in patients who are HIV positive', 'role': 'assistant'}]