On this question I was between (C) and (A) and I ended up incorrectly picking (C). Now I think I see why it is wrong. Paragraph 4 isn't discussing WHEN native Americans began to distinguish between intertribal and tribal tendencies, which is what (C) is saying.
I definitely see that (A) is the best answer but I want to be sure I know why.
I think (A) is correct because paragraph 4 acknowledges that intertribal activities are a significant part of native American culture and then provides examples. When the author follows this by saying that, "cultural borrowing is, of course, old news" he is using cultural borrowing to mean intertribal activities. So if intertribal activities have been around for a while then it makes sense that their existence would be "unsurprising" at powwows (what (A) is saying).
Is my thinking correct here? I would appreciate any help!