The correct answer is: A. Lack of antigen in his blood.
A person with AB blood group has both A and B antigens on the surface of their red blood cells, but they do not have any antibodies against either A or B antigens. This means that they can receive blood from any blood group, as their body will not reject the donated blood.
Blood type is determined by the presence or absence of certain antigens on the surface of red blood cells. There are four main blood types: A, B, AB, and O. People with type A blood have A antigens on their red blood cells, people with type B blood have B antigens, people with type AB blood have both A and B antigens, and people with type O blood have neither A nor B antigens.
In addition to antigens, blood also contains antibodies. Antibodies are proteins that the body produces to fight off infection. If a person receives blood that contains antigens that their body does not have, their immune system will attack the donated blood. This can lead to a serious condition called transfusion reaction.
Because people with AB blood do not have any antibodies against A or B antigens, they can receive blood from any blood group. This makes them universal recipients. However, people with AB blood can only donate blood to other people with AB blood.
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