Hi @hallerae, thanks for your post. The stimulus presents an argument. The conclusion is "it is clear that even 12,000 years ago human activity was causing the extinction of animal species." The premises provided in support are (1) that humans began to spread across North America (2) as the climate became warmer (3) and during the same period certain large mammals became extinct.
The flaw here is that the premises themselves provide an alternative cause - rather than humans, the extinctions may have been caused by a warming climate. Answer choice (E) correctly identifies this problem.
Answer choice (C) is entirely irrelevant to this particular argument. The "significance" of the extinctions then vs. now has no bearing whatsoever on the strength or weakness of the conclusion in this stimulus. The question is whether human activity (rather than climate change) caused the extinctions, period.
Hope this helps! Please let us know if you have any additional questions.
