Which Scenario Best Illustrates the Concept of Migration

Which scenario best illustrates the concept of migration?

A) Twelve thousand years ago Native Americans traversed the Bering Strait to settle in the Americas, causing different genetic traits to be favored over others.
B) The genetic mutation that causes sickle cell anemia also increases resistance to malaria, increasing the frequency of the diseased allele in the general population.
C) The prevalence of depression is greater in populations where the serotonin transporter gene translocated to position q21 along chromosome 17.
D) There is a higher than average rate of Ellis-van Creveld syndrome in the Amish community because the diseased allele was introduced by some original Amish settlers.