Final answer:
The end of the ice age caused climate changes and resource availability issues that led Native American tribes to develop agriculture as a new method for survival.
Step-by-step explanation:
The end of the ice age prompted Native American tribes to experiment with growing new crops and becoming farmers primarily due to climate changes and resource availability (B). After the ice age, the environment became more conducive to agriculture, with more arable land and favorable conditions for crop growth. The shift in climate altered animal migration patterns, leading to a scarcity of game for hunting. These changes likely put a strain on food resources and compelled tribes to develop new survival strategies such as plant domestication and agriculture.
As large ice-covered areas melted, they became forested or farmed, necessitating a shift from a nomadic lifestyle to one of settled farming communities to ensure consistent food supply. The process of plant domestication may have started accidentally as gathered seeds grew where they were discarded, which, over time, resulted in more intentional farming practices.
Furthermore, climate conditions that brought about drier conditions may have forced early humans to intervene in plant growth to sustain their populations— a critical step toward the development of agriculture. This transition was a major cultural revolution and had a profound impact on the social structure and future developments of Native American tribes.