A person with unknown blood group under $A B O$ system, has suffered much blood loss in an accident and…
A person with unknown blood group under $A B O$ system, has suffered much blood loss in an accident and needs immediate blood transfusion. His one friend who has a valid certificate of his own blood type, offers for blood donation without delay. What would have been the type of blood group of the donor friend?
Type $A B$
Type $\mathrm{O}$
Type $\mathrm{A}$
Type B
Solution
Blood type ' $\mathrm{O}$ ' has no any antigen but both types of antibodies ' $a$ ' and ' $\mathrm{b}$ '. The person with blood type ' $O$ ' is universal donor.