The correct option is A Genetic drift
Change in allele frequencies of a population that occurs by chance is called genetic drift. When a random section of population migrates to another new area, allele frequencies change in the original as well as in the new population. Sometimes the change in allele frequency is so different in the new sample of population that they become a different species. The original drifted population, in such cases, becomes founders and the effect is called founder effect. Hence, founder effect is a consequence of genetic drift.
Natural selection is a process in which heritable variations enabling better survival are enabled to reproduce and leave greater number of progeny.
Genetic recombination is a process in which segments of DNA are broken and recombined to produce new combinations of alleles. It introduces variations in a population.
Mutation refers to the change in the nucleotide sequence of genetic materials like DNA and RNA.