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': "True about widal test: \nSelect and explain. \nA. Anti-0 antibody persists longer, B. 0 antigen of S. paratyphi is used, C. H-antigen is most immunogenic, D. Felix tube is used for 'H' agglutination lnar", 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is. 'c' i. e., H-antigen is most immunogenic", 'role': 'assistant'}]