The correct option is A ABO blood groups
A gene can have many different alleles within a population. A single organism can only have two alleles because it receives one from each of its parents. However, in a population, there can exist many different forms of a gene. Having multiple alleles for a gene leads to things like many different kinds of hair color and body size. Blood type A, B and O are the three alleles that can come together in different ways to make different blood types: AB, AA, BB, OO, AO and BO. Hence, ABO blood groups is an example of multiple alleles.