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': 'Absence of Vi-antibody in a typhoid patient has: \nSelect and explain. \nA. Good prognosis, B. Bad prognosis, C. No relation with prognosis, D. Indicates widal negative', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is. 'b' i. e., Bad prognosis", 'role': 'assistant'}]