Please find below the solution to the asked query
Antibodies are generated in response to antigens. Blood group O does not have any antigen. But people with this blood group must have come in contact with some other antigen like during bacterial infection or viral infection before. Because of these antigens anti-A and anti-B antibodies are formed in their blood. In this case, antibody formation is not directed by the antigens present on the surface of RBCs.
People with O blood group do not have antigen responsible for either A,B or AB blood group because the enzymes responsible for the synthesis of antigen is not functional.
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