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': 'Pneumococcal vaccine is prepared from ? \nSelect and explain. \nA. Cell surface antigen, B. Capsular polysaccharide, C. From exotoxin, D. From M protien', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Capsular polysaccharide", 'role': 'assistant'}]