This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'Symptoms of C. botulinum food poisoning include double vision, inability to speak, and respiratory paralysis. These symptoms are consistent with \nSelect and explain. \nA. Invasion of the gut epithelium by C. botulinum, B. Secretion of an enterotoxin, C. Endotoxin shock, D. Ingestion of a neurotoxin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Clostridium botulinum growing in food produces a potent neurotoxin that causes diplopia, dysphagia, respiratory paralysis, and speech difficulties when ingested by humans. The toxin is thought to act by blocking the action of acetylcholine at neuromuscular junctions. Botulism is associated with high mortality; fortunately, C. botulinum infection in humans is rare.', 'role': 'assistant'}]