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: Social & Preventive Medicine
[{'content': 'Meningococcal vaccine is available for all of the following, except - \nSelect and explain. \nA. Group A, B. Group B, C. Group C, D. Group Y', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Group B o Vaccines are available for group A, C, Y and W-125. There is no group B vaccine available at present.", 'role': 'assistant'}]