Final answer:
There are four major blood groups: A, B, AB, and O. The ABO blood group system determines these types based on the presence or absence of A and B antigens on red blood cells. The Rh blood group system has five main antigens, with the D antigen being the most significant one.
Step-by-step explanation:
The major blood groups are determined by the ABO blood group and the Rh blood group systems. The ABO blood group system consists of four types: A, B, AB, and O. Blood type A has the A antigen, blood type B has the B antigen, blood type AB has both A and B antigens, and blood type O has neither A nor B antigens. The Rh blood group system has five main antigens, with the D antigen being the most significant one.