The best example of a perceptual region from the options provided is:
B. The "Sun Belt" in the United States, a region characterized by a warm climate and a perceived culture of economic growth and migration.
Perceptual regions are defined by people's feelings, attitudes, and beliefs about the area, rather than strict physical or political boundaries. The "Sun Belt" is characterized by a shared perception of climate and socio-economic characteristics, making it a quintessential example of a perceptual region.