This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fluid and electrolytes, Subject name: Medicine
[{'content': 'The maximum concentration of potassium delivered central line is \nSelect and explain. \nA. 20 mmol/L, B. 40 mmol/L, C. 60 mmol/L, D. 80 mmol/L', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In adults, the preferred concentration central line is 20 mEq/100 ml. The maximum concentration for fluid restricted patients is 20 mEq/50 ml. Ref Davidson 23rd edition pg 345', 'role': 'assistant'}]