This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Asthma, Subject name: Pharmacology
[{'content': 'Theophylline therapeutic blood ranges \nSelect and explain. \nA. 0-5, B. 10-May, C. 15-May, D. 20-May', 'role': 'user'}, {'content': 'Answer: D \nExplanation: (5-20) (221-KDT6th)* Therapeutic ranges 5-20 as shown in above figure* Theophylline has a narrow margin of safety. Dose dependent toxicity starts from upper part of therapeutic concentration', 'role': 'assistant'}]