Microbiology General 01c8b111 Which is true about Widal reaction - A Antibody to H Ag appears first and persists B Antibody to 0 Ag appears first and persists C Antibodies to H & 0 Ag appears simultaneously and persists D None of the above High-Yield Explanation Ans. is 'a' i.e., Antibody to 'H' antigen appears first and persists