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': 'Although tetracycline is a broad-spectrum antibiotic but resistance to the drug developed by the following mechanism: \nSelect and explain. \nA. By inactivating enzymes., B. An efflux pump mechanism., C. Alteration of the binding site., D. Absence of a metabolic pathway.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Tetracyclines are broad-spectrum bacteriostatic drugs. Development of resistance to\xa0 tetracyclines are mainly due to the development of efflux pumps.', 'role': 'assistant'}]