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: Pharmacology
[{'content': 'Following serum levels are suggestive of lithium toxicity \nSelect and explain. \nA. 2 mEq/L, B. 4 mEq/L, C. 6 mEq/L, D. 8 mEq/L', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a. 2 mEq/L', 'role': 'assistant'}]