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': 'WHO formation day is \nSelect and explain. \nA. 5-May, B. 7 April, C. 10-Jun, D. 10-Jul', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]