It's probably c. But be sure to check your assigned reading to be sure.
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Which of the following best describes the evolution of pre-historic Native American cultures in North America?
a. As the glaciers receded, many useful technologies were uncovered and prehistoric people were able to live good lives.
b. As weapons became better, Native Americans could hunt enough game to feed larger groups of people.
c. As the weather warmed, Woodland Indians could no longer hunt for wooly mammoth and other large game so they began gathering plants to eat.
d. As technology improved and knowledge of agriculture developed, the population of pre-historic cultures increased and civilizations developed.
2 answers
http://www.cabrillo.edu/~crsmith/anth7_archaic.html