4 is weird too!

Confused about the either/or bit here; in logic games, I'm pretty sure we understand either x or y to encompass three possibilities: only x, only y, x and y. But here, I don't really see how we can abandon the notion and reject Mather's definition. What am I missing?

#help (Added by Admin)

I think the difference here is between surveys and observable phenomena. We're meant to question surveys by default since there are a million ways a survey could be flawed. On the other hand, observable phenomena are empirical occurrences that are unquestionable by default. This question is a frustrating one though; I got it wrong for a different reason lol.

Proof by contradiction

following since I have a similar problem

Good question, I crossed out D for the same reason