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': 'Action of theophylline is reduced by ? \nSelect and explain. \nA. Smoking, B. Erythromycin, C. Cimetidine, D. Lithium', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Smoking", 'role': 'assistant'}]