To which blood group do universal recipients belong?

Analyze the question: The question asks which blood group is the universal recipient, meaning the group that can receive blood from all other ABO groups.

Concept: Blood groups are defined by the antigens on red blood cells and the antibodies in the plasma:

| Blood group | Antigens on red cells | Antibodies in plasma | |---|---|---| | A | A | anti-B | | B | B | anti-A | | AB | A and B | none | | O | none | anti-A and anti-B |

A transfusion fails when the recipient's plasma antibodies attack antigens on the donor's red cells, causing agglutination (clumping).

Solution:

1. Group AB has both A and B antigens, so it has no anti-A or anti-B antibodies in its plasma.
2. With no antibodies to attack donor cells, AB can safely receive blood from A, B, AB and O.
3. So AB is the universal recipient.
4. Group O is the universal donor, because its red cells carry no A or B antigens. It is a common trap in this question (option C).

Answer: The correct option is D (AB).

Tip: Remember "AB = Accepts all, Blood from anyone" and "O = Offers to all." Universal donor is O, and universal recipient is AB.