The correct answer is: A. Group A only
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 the A antigen on their red blood cells, people with type B blood have the B antigen, people with type AB blood have both A and B antigens, and people with type O blood have neither A nor B antigens.
When blood is transfused, it is important to match the blood type of the donor to the blood type of the recipient. This is because the immune system can attack red blood cells that have different antigens. If a person with type A blood receives type B blood, their immune system will attack the B antigens on the donor’s red blood cells, and this can lead to serious complications, including death.
Therefore, the only blood type that can be safely transfused into a person with type A blood is type A blood.