This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Pharmacology
[{'content': 'Antimicrobials effective against anaerobic bacteria include the following EXCEPT: \nSelect and explain. \nA. Tobramycin, B. Clindamycin, C. Chloramphenicol, D. Metronidazole', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Ref: KDT 6/e p719, 720) Aminoglycosides require oxygen for transpo in the bacterial cell. These are therefore ineffective against anaerobic organisms.', 'role': 'assistant'}]