Question

what are the four main blood groups?
o a b ab o
o a b o
o ab o rr
o b ab o d
o a o b m

Explanation:

Blood groups are classified based on the presence or absence of certain antigens. The ABO blood group system is the most important one for transfusion. In this system, the four main blood groups are A, B, AB, and O.

Answer:

A. A, B, AB, O