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': 'ORS required during first 4 hours in a 20 kg child - \nSelect and explain. \nA. 200-400 ml, B. 400-600 ml, C. 600-800 ml, D. 1200-2200 ml', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]