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': 'Theophyline levels in blood are increased by: \nSelect and explain. \nA. Barbiturates, B. Methotrexate, C. Cimetidine, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cimetidine', 'role': 'assistant'}]