Final answer:
Adobe is the most suitable material for building homes in the desert southwest, offering excellent insulation and being made from locally available and sustainable resources.
Step-by-step explanation:
The most suitable material for building homes in the desert southwest is adobe. Adobe is a material made from sun-dried mud bricks and has been historically used both by indigenous peoples of the American Southwest and Mesoamerica, as well as being influenced by Spanish colonial architecture. Adobe walls are thick, providing excellent insulation against the extreme heat encountered during the day, and releasing stored heat during the cooler evenings. Moreover, the near-flat roofs of traditional adobe houses are designed to collect rainwater or morning dew, which is a beneficial adaptation to the dry climate of the area. The materials required to build with adobe are locally available and sustainable, contrasting with imported and expensive materials such as cement and steel that can make homes less comfortable in the local environment.