Based on the provided passage about the Mound Builders, they primarily lived in regions from the Great Lakes to the Gulf of Mexico, and east of the Mississippi River to the Appalachian Mountains.
Assuming the regions on the map correspond to these geographic areas, the Mound Builders would primarily inhabit:
- Region A (if it represents the area east of the Mississippi River)
- Region B (if it encompasses the southern regions towards the Gulf of Mexico)
Without the exact representation of the regions on the map, this is the most likely answer based on the provided information. So, please select the regions that fit this description accordingly.