Which of the following best illustrates multiple alleles?

The ABO blood type system is an excellent illustration of multiple alleles because it involves more than two alleles for a single gene. In this system, there are three alleles: A, B, and O. An individual can inherit any combination of these alleles, resulting in four possible blood types: A, B, AB, and O. Each blood type arises from the different combinations of these alleles and their relationships, with A and B being codominant and O being recessive to both. The presence of multiple alleles allows for a greater variety of phenotypes than would be possible if there were only two alleles.

In contrast, traits influenced by one gene or those determined solely by dominant alleles do not represent the concept of multiple alleles. Similarly, expression based on parental genes lacks the necessary diversity that multiple alleles provide. Therefore, the ABO blood type system stands out as the best example of how multiple alleles function in determining genotypic and phenotypic expression.