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: Microbiology
[{'content': 'Clostridium botulinum toxin mode of action is by: March 2012 \nSelect and explain. \nA. Presynaptic block, B. Postsvnaptic block, C. Competitive inhibition of acetylcholine, D. Destruction of acetylcholine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: A i.e. Presynaptic block Cl. Botulinum toxin acts by blocking the production/ release of acetylcholine at the synapses & neuromuscular junctions', 'role': 'assistant'}]