Yerky presents evidence (the lab experiment results) that supports a conclusion that contradicts Xu’s conclusion. Yerky concludes squirrel blood doesn’t have a substance that keeps it from freezing at water temperature. This contradicts Xu’s conclusion.

Yerky doesn’t comment on the way in which Yerky’s evidence was gathered. We don’t know why Xu thinks that a squirrel’s blood doesn’t freeze during hibernation, or that a squirrel’s blood gets colder than the freezing temperature of water during hibernation.

Yerky probably doesn’t agree that a squirrel’s blood fails to freeze at the freezing temperature of water. The lab tests show that it does freeze at that temperature. So there’s no way that Yerky provides an explanation for a phenomenon that she doesn’t even think happens.

None of the terms in Xu’s argument is used ambiguously. “Hibernation” means the same thing throughout Xu’s argument. Same with “blood” and “freezing” and “temperature” and every other word.

Yerky brings up lab results that suggest Yerk’s conclusion is wrong. But this doesn’t mean Xu’s evidence has no bearing (i.e. is irrelevant.) Evidence can be relevant, even if its ultimately not persuasive.