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': 'Cholera toxin is due to - \nSelect and explain. \nA. Chromosome, B. Plasmid, C. Phage, D. Transposons', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]