ABO blood grouping show phenotypes and genotypes respectively-
6,2
6,4
3,6
4,6
ABO blood grouping show 4 phenotypes i e., Blood group A, blood group B, blood group AB, blood group O.
There are total 6 genotypes for ABO blood grouping. Two genotypes for blood group A, two for blood group B,one for blood group AB and one for blood group O and these are total 6 genotypes.
Option 4 is the correct answer.