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': 'In a patient of chronic asthma on treatment with theophylline, which of the following should not be used to treat his upper respiratory tract infection? \nSelect and explain. \nA. Ampicillin, B. Cephalexin, C. Erythromycin, D. All', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]