ABO blood group is controlled by more than two alleles in a population, this shows that ABO blood group is an example of:

polygenic inheritance

operans

multiple alleles

allelic interaction

The gene responsible for the ABO blood group system is I.

This gene exists in three allelic forms - IA, IB, and i. IA and IB are dominant alleles and i is the recessive allele.

Since three alleles for the ABO blood group are found in a population, it is an example of multiple alleles.