<prompt> Although more than 400 blood groups have been identified,the ABO blood group system remians the mostimpoant in clinical medicne because :It was the first blood group system to be discoveredIt has four different blood groups A,B, AB, O H.ABOH antigens are present in most body tissues and fluids.ABOH antibodies are invariably present in plasma when persons RBC lacks the corresponding antigen  <response>: . ABOH antibodies are invariably present in plasma when persons RBC lacks the corresponding antigen 