Final answer:
Mutation and sexual reproduction are the two primary sources of genetic variation, hence answer is not provided in the options.
Step-by-step explanation:
The two primary sources of genetic variation are mutation and sexual reproduction. Mutations are changes in the DNA sequence, and they are the fundamental source of new genetic diversity. They can result in new alleles or traits within a population, affecting an organism's phenotype in various ways.
Mutations might lead to a phenotype with improved fitness, reduce an organism's chance of survival, or may have no appreciable effect at all, which are termed neutral mutations. In addition to mutation, sexual reproduction contributes to genetic variation by creating unique combinations of alleles as genes from two parents recombine.
This recombination process results in offspring with a mix of genetic traits distinct from both parents and any siblings.