Universal blood donor will be a blood group of:
**Core Concept**
The universal blood donor is a blood group that can be transfused to any individual without causing a hemolytic reaction, regardless of their ABO blood group. This is due to the absence of A and B antigens on the surface of red blood cells.
**Why the Correct Answer is Right**
The correct answer is **ABO blood group O**. This is because group O individuals lack A and B antigens on their red blood cells, making their blood compatible with all other ABO blood groups. When an individual with blood group O donates blood, their red blood cells do not have A or B antigens, which eliminates the risk of an immune response against the recipient's A or B antigens. This is because the immune system of the recipient will not recognize the absence of A or B antigens as foreign.
**Why Each Wrong Option is Incorrect**
**Option A:** **AB**. While AB individuals have both A and B antigens on their red blood cells, they can still donate blood to individuals with A and AB blood groups, but not to those with B and O blood groups.
**Option B:** **A**. Individuals with blood group A have A antigens on their red blood cells, making their blood incompatible with B and AB blood groups.
**Option C:** **B**. Similarly, individuals with blood group B have B antigens on their red blood cells, making their blood incompatible with A and AB blood groups.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that individuals with blood group O are not only universal donors but also universal recipients, as they lack A and B antibodies in their plasma.
**Correct Answer:** D. O