In human blood grouping, people with which ABO blood group are called universal recipients because they can receive blood from all other groups?

Introduction / Context:
Blood transfusion is a critical medical procedure, and compatibility between donor and recipient blood groups is essential for safety. In the ABO blood group system, some groups can donate to many others, while some can receive from many groups. The term universal recipient is used for a particular group that can accept blood from all other ABO groups under ideal conditions, and this concept is frequently tested in general science and biology questions.

Given Data / Assumptions:
The question asks which blood group is known as the universal recipient.
Options include blood groups O, A, B, and AB.
We assume only the ABO system and ignore the Rh factor for simplicity at school level.
The concept is based on the presence or absence of A and B antigens and corresponding antibodies in the blood.

Concept / Approach:
In the ABO system, red blood cells can have A antigen, B antigen, both, or neither. Blood group AB has both A and B antigens on the surface of its red blood cells and does not have anti A or anti B antibodies in the plasma. Therefore, an AB individual can receive red blood cells from donors with groups A, B, AB, or O without their plasma antibodies attacking the donor cells, at least from the ABO compatibility perspective. This is why group AB is called the universal recipient. Group O, on the other hand, is considered the universal donor because its red blood cells lack A and B antigens.

Step-by-Step Solution:
Step 1: Recall the antigens present on red blood cells and antibodies in plasma for each ABO group. Step 2: Note that group AB has both A and B antigens and lacks both anti A and anti B antibodies. Step 3: Understand that without these antibodies, the recipient plasma will not attack incoming donor red blood cells of any ABO type. Step 4: Conclude that group AB is the universal recipient in the ABO system.

Verification / Alternative check:
You can support this by looking at standard ABO compatibility charts used in hospitals. These charts usually show that AB can receive from A, B, AB, and O. In practice, doctors also consider the Rh factor, and the safest transfusion is always matching the exact group. However, for school level theory, AB is widely labeled the universal recipient.

Why Other Options Are Wrong:
Blood group O has no A or B antigens but has both anti A and anti B antibodies, so it can donate to many groups but cannot receive safely from all, so it is not the universal recipient.
Blood groups A and B each have one type of antigen and the corresponding opposite antibodies, so they can only receive from compatible groups and are not universal recipients.

Common Pitfalls:
Students often confuse universal donor and universal recipient and may mistakenly choose group O for both concepts. Remembering that O donates widely because its cells carry no antigens, while AB receives widely because it has no antibodies, helps avoid this confusion. Also note that real clinical practice uses more detailed matching, but the exam concept remains the same.

Final Answer:
The universal recipient in the ABO system is Blood group AB.