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': 'The infectivity, of chicken pox lasts for - \nSelect and explain. \nA. Till the last scab falls off, B. 6 days after onset of rash, C. 3 days after onset of rash, D. Till the fever subsides', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., 6 days after onset of rash", 'role': 'assistant'}]