Blood types are determined by the proteins present on the surface of the red blood cells.
• In blood type A, red cells have A antigens and there are anti-B antibodies in the plasma.
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• Blood type B has B antigens and anti-A anitbodies
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• Blood type AB has A and B antigens and no antibodies
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• Blood type O, has ,no antigens ,and ,both anti-A and anti-B antibodies.
Is important not to pair antigens and antibodies, as the antibodies of the recipient will attack the antigens.
For example, if a person with O blood type receives AB blood, the patient's anti-A and anti-B antibodies would attack the donor's blood because the red cells have A and B antigens.
This means that a person with O blood type can only receive blood type O because those red cells don't have any antigens on their surface (option b).