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': 'All the following drugs act on the Microtubular Protein Tubulin EXCEPT: \nSelect and explain. \nA. Colchicine, B. Vincristin, C. Bleomycin, D. Paclitaxel', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Bleomycin', 'role': 'assistant'}]