Final answer:
Directional stabilization, or directional selection, is a type of natural selection where one phenotype is favored, leading to a shift towards that phenotype and potentially resulting in greater genetic variance within the population.
Step-by-step explanation:
Directional stabilization, also known as directional selection, is a type of natural selection where one extreme phenotype is favored over other phenotypes, leading to a shift in the population's phenotypic distribution towards that extreme.
This is in contrast to stabilizing selection, where intermediate phenotypes are favored and phenotypic variation decreases. The result of directional selection on variation is a reduction in the overall genetic variance. An example of directional selection can be seen in the beak sizes of Galápagos finches, where certain beak sizes may become more favorable due to environmental changes, leading to a population shift towards that size.
Answering the question, type b, directional selection, results in greater genetic variance in a population, as it favors a specific phenotype and thus can lead to increased variation as that phenotype becomes more common.