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': 'Bacitracin acts on : \nSelect and explain. \nA. Cell wall, B. Cell membrane, C. Nucleic acid, D. Ribosome', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Bacitracin acts by inhibiting the synthesis of the cell wall.\nOther polypeptide antibiotics like polymyxin B, colistin and tyrothricin act by an affecting membrane.', 'role': 'assistant'}]