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': 'Blockade of neuromuscular transmission by botulinum toxin is an example of: \nSelect and explain. \nA. Depolarizing blockade, B. Competitive blockade, C. Presynaptic blockade, D. Postsynaptic blockade', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]