This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': 'Cholera is caused by- \nSelect and explain. \nA. V.cholerae O1, B. V.cholerae O1 and O139, C. V. cholerae O139, D. NAG vibrios', 'role': 'user'}, {'content': "Answer: B \nExplanation: Vibrio cholerae is sero-grouped on the basis of 'O' antigen into several 'O' serogroups. Of these, O1 and O139 produce the cholera toxin. Hence cholera is caused by only these 2 serogroups ( as only that enteritis is called cholera which is due to cholera toxin )", 'role': 'assistant'}]