The latter two paragraphs look at an empirical implication of the claim that people have adapted to eating cooked food. That is, they explore what must have been the case if it is correct that we have adapted. They do this by looking at the necessary evolution, and the evidence for that evolution. I don't love the phrasing of empirical implication, but it does technically describe the passage.
The issue with C is that I don't think the second paragraph explores an objection to the claim. I think the second paragraph is just asking how it happened, and exploring the physical changes we are able to see from the evidence.
