Final answer:
Mississippian settlements commonly shared access to water resources like rivers, which provided fertile soil for agriculture and routes for trade, contributing to the growth and complexity of their society.
Step-by-step explanation:
Mississippian settlements had several commonalities, but what they all had in common according to the provided options is their access to water resources; specifically, their proximity to rivers. Rivers provided a reliable source of water for both domestic use and agricultural abundance due to the fertile soil deposited along riverbanks. These locations were also ideal for the development of trade, as waterways played a significant role in transportation and communication networks. The availability of fertile soil, water for irrigation, and facilitation of trade would have supported larger populations and the growth of complex societies characterized by the Mississippian culture.