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': 'New WHO ORS osmolarity is \nSelect and explain. \nA. 245, B. 270K. Park 22/e p203, C. 290, D. 310', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]