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': 'Drugs which increase the level of theophylline include : \nSelect and explain. \nA. Ciprofloxacin, B. Cimetidine, C. Allopurinol, D. All of these', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Drugs which inhibit theophylline metabolism and increase its plasma level are:\n\n\nErythromycin\nCiprofloxacin\nCimetidine\nOCP\nAllopurinol\n\n\nAgents which induce theophylline metabolism and decrease its plasma level are :\n\n\nSmoking\nPhenytoin\nRifampicin\nPhenobarbitone', 'role': 'assistant'}]