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: Social & Preventive Medicine
[{'content': 'Which ARV has been recommended by WHO as the most effective - \nSelect and explain. \nA. Duck cell vaccine, B. Chick fibroblast vaccine, C. HDCV, D. Sheep brain vaccine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]