The factor that best explains why Native Americans were able to make permanent settlements that included features like the Etowah Mounds is:
A. Native Americans began to cultivate plants for food.
The ability to cultivate plants allowed Native Americans to settle in one place, as they no longer needed to follow migrating animal herds. This agricultural development enabled the establishment of permanent communities and the construction of significant structures like mounds, which served various social, religious, and ceremonial purposes.