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': 'TDM is a process where plasma concentration of drug is constantly monitored. Recommended levels of plasma concentration for Theophylline is \nSelect and explain. \nA. 10 - 20 mg / ml, B. 10 - 45 mg / ml, C. 4 - 12 mg / ml, D. 8 - 15 mg / ml', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]