From the local monuments, some of which, as the enclosures and other mural works, are yet to be described, we learn much in regard to the people by whom they were built. The builders of the Cahokia group, which includes the giant mound of its type, also of the Etowah group in northeastern Georgia, and the Rich Woods cluster of southeast Missouri, must have been sedentary or at least substantially so, depending to a large extent upon the cultivation of the soil for subsistence. –W. J. McGee and Cyrus Thomas Prehistoric North America (1905) Based on the excerpt, which best explains the development of permanent and semi-permanent American Indian settlements from the Mississippi River to the East Coast? a Increased contact with neighboring communities due to the domestication of the horse enabled regional tribes to rely more heavily on trade for food and other goods; permanent settlements facilitated trade. b Development of farming methods and domestication of crops and animals enabled a reduction in dependence on hunting and gathering for food; greater dependence on agriculture reduced the need to follow herds of wild game. c Threats of raids by more militaristic tribes during times of prosperity prompted small kin-based groups to ally with one another for mutual protection; these small groups built larger communities to combine resources and deter attack. d The religious beliefs of some local cultures revealed certain sites to be sacred places, where leaders were interred at the end of their lives; these sacred sites were built upon and maintained by the community, leading to permanent settlement.