Which of the following best explains the widespread decline in Indigenous populations after the arrival of Spanish conquistadors? inability to connect with global markets inability to connect with global markets natural disasters natural disasters disease and environmental changes disease and environmental changes fighting and lack of guns

The most accurate explanation for the widespread decline in Indigenous populations after the arrival of Spanish conquistadors is "disease and environmental changes." The Spanish conquest brought with it diseases, such as smallpox, to which the Indigenous populations had no immunity. This resulted in devastating epidemics that decimated their numbers. Additionally, the arrival of the conquistadors also led to significant environmental changes, including disruptions to indigenous agricultural practices and land use, which further contributed to population decline. The other options (inability to connect with global markets, natural disasters, and fighting and lack of guns) may have had some impact but are not as significant as disease and environmental changes.