<em>Directional selection, </em><em>in population genetics, is also denoted as positive selection and is described as a mode of 'natural selection' whereby a particular extreme phenotype is being favored or privileged as compared to that of the other phenotypes, that often leads to the 'allele frequency' to change or shift over a period in time in the same direction of that particular phenotype.</em>
<em><u>The correct answer to the question above is directional selection.</u></em>