Distinguish between: Polygenic inheritance and Multiple allelism.

(N/A) Polygenic Inheritance: This refers to a trait that is controlled by two or more genes,often resulting in a continuous range of phenotypes. Examples include human skin color and height.
Multiple Allelism: This refers to the presence of more than two alleles for a single gene locus within a population. While an individual carries only two alleles,the population exhibits multiple variations. $A$ classic example is the $ABO$ blood grouping system in humans.