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: Medicine
[{'content': 'Infectivity of chicken pox is seen- \nSelect and explain. \nA. Till last scab falls off, B. 3 days after the appearance of rash, C. 6 days after the appearance of rash, D. As long as the fever lasts', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]