To discuss why (C) is incorrect, note first that the author never makes the claim that the archaeological evidence lends itself to a multi-purpose understanding of clearings. In line 8, for example, archaeological evidence is described as circumstantial, and archaeological evidence isn't really mentioned afterwards. The fact that it is barely mentioned also suggests that the main idea of the passage is not to discuss archaeological evidence that supports a multi-purpose understanding of clearings.
As for why (B) is correct, we can see at the beginning that the author tells us that the resource-procurement model is widely accepted. But by the end of the second paragraph, the author suggests that available evidence provides support for another, "non economic" (line 26) model. The last paragraphs help explain what this alternate model is. Hope this helps!
