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': 'Which among the following drug is safest in a patient allergic to penicillin: \nSelect and explain. \nA. Cephalexin, B. Imipennem, C. Cefepime, D. Aztreonam', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Aztreonam', 'role': 'assistant'}]