<prompt> A 40 year old female patient presents with excessive bleeding. Patient gives a history of road traffic accident 5 hours ago and had a lacerated wound on lower back region. Blood grouping test reveals presence of Anti A antibody, Anti B antibody, Anti H antibody and Anti Rh D antibody in the serum. This patient can receive transfusion from a donor having blood group:O positiveO negativeAB positiveBombay blood group  <response>: Apart from A B and O, RBC of type O contains large amount of another antigen called H substance. H substance is genetically different from ABO, but is a precursor of A and B antigens. An O group individual who inherits A or B genes but fails to inherit H gene from either parent is called Oh phenotype or Bombay blood group. 