O- is universal donor.

• A. Universal recipient
• B. Universal donor
• C. Rare
• D. Common

Answer: (B)

The key idea is blood compatibility for red blood cell transfusions. O negative blood carries no A or B antigens and also lacks the Rh (D) antigen on the surface of its red cells. Because of the absence of these antigens, O negative red cells can be given to patients of almost any ABO type and Rh status without triggering antibodies against A, B, or D. In urgent situations where a patient’s blood type isn’t yet known, this makes O negative the safest default choice for transfusing red cells.

It’s important to note that being universal for red cell transfusions does not apply to plasma components. For plasma, AB is the universal donor. Also, O negative blood is relatively rare in the population, so while it’s the go-to in emergencies, access isn’t universal in everyday care.

So the statement that O negative is universal donor best captures why this type is used when compatibility needs to be sure and quickly established.