Final answer:
The fourth source region for folk house styles in the United States and Canada, alongside Northern, Middle Atlantic, and Southern Coastal, is the Western Plains. Additionally, the cultural practice of potlatch is associated with the Pacific Northwest.
Step-by-step explanation:
The four source regions for folk house styles for much of the United States and Canada are Northern, Middle Atlantic, Southern Coastal, and Western Plains. The answer to this fill-in-the-blank question is a) Western Plains. Folk housing in the middle US evolved significantly in the Middle Atlantic States and diffused from there into other regions, including the Midwest and southern areas.
Folk houses in the Middle Atlantic region were influenced by a diverse set of cultures from continental Europe and Africans, which contributed to the development of a versatile folk culture. This culture spread westward into the Great Valley, across the Appalachian Mountains, and into the Midwest.
The migrants carried with this their cultural traditions, including architectural styles like the Hall and Parlor house and the I-house which are common in the Mid-Atlantic and Midwest. For the practice of potlatch, associated with the Pacific Northwest, the correct answer to the second question is d) The Pacific Northwest. This cultural practice reflects the unique social structures and traditions of the region.