Answer: III.mutations
Genetic variation can be defined as genetic differences that occurs within a population. Genetic variations are the differences in DNA segments or genes that occur in a population. The genetic variations makes individuals different from each other at the genetic or genomic level. Mutation is an alteration in the genetic material of an organism. A mutation can occur when the DNA is being copied during replication or because of environmental factors. Mutations contributes to genetic variability within a population.