This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition, Subject name: Pediatrics
[{'content': 'Persistent diarrhoea is defined as diarrhoea lasting more than? \nSelect and explain. \nA. 7 days, B. 14 days, C. 21 days, D. 28 days', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) 14 days', 'role': 'assistant'}]