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': 'Concentration of sodium in low osmolar ORS is: \nSelect and explain. \nA. 45, B. 75, C. 90, D. 60', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 75', 'role': 'assistant'}]