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: Physiology
[{'content': 'Calcute the osmolarity of normal saline ______ \nSelect and explain. \nA. 333 mOsmol / L, B. 300 mOsmol / L, C. 280 mOsmol / L, D. 320 mOsmol / L', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]