Question

Which blood group is known as the Universal Donor?

• A. A negative
• B. B negative
• C. O negative
• D. AB positive

Hint:

Remember the donor/recipient mnemonic:
O Negative ($O^-$): Universal Donor (No antigens to trigger immune attacks).
AB Positive ($AB^+$): Universal Recipient (No antibodies to attack foreign blood).

Answer 1

The Correct Option is C

Step 1: Recall the donor rule.
A universal donor should not have major antigens on the red blood cell surface, because those antigens can trigger a reaction in the recipient.

Step 2: Apply ABO and Rh grouping.
O group has no A or B antigen. Rh negative has no Rh antigen. So O negative has the least antigen risk during emergency transfusion.

Step 3: Pick the answer.
Therefore, O negative is known as the universal donor blood group.
\[ oxed{ ext{Option 3: O negative}} \]