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': 'Co-receptor for R5 variant of HW virus: \nSelect and explain. \nA. Integrin, B. CCR 5, C. CXCR 4, D. P 53', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. b. CCR5', 'role': 'assistant'}]