Like many of you, I've been using the PS LR Bible to study and I've run into something that I can't quite figure out on my own. If you know where I got confused, can you help me out and explain it to me?

Here we go: In the weaken section, the bible gives us a question that essentially says: "x -> y (conditional)"; Weaken this. The correct answer choice says "x happened and z happened (as in y didn't happen)". I understand how this weakens the original conclusion x -> y. If you can show x (the sufficient) happening and y (the necessary) didn't happen, this would weaken the conclusion (since the conclusion says if x then y).

Where I'm confused is why another answer choice is wrong. The other answer choice essentially says "y -> not x" Why is this wrong? The contrapositive of this is the same thing as the correct answer choice (x -> not y).

What I'm trying to do is figure out what the answer commonly is and what the trap answer commonly is in weaken questions that have conditional conclusions. If the conclusion is x->y, I should actively search for the answer choice that says x->not y. According to the question, I should avoid y->not x, but that doesn't seem to make sense.

I'm not sure how copyright stuff works, but I'm referring to the question on page 180 of the bible. If this could get me in trouble, let me know asap so I can edit my post.

So, can someone complete this in conditional terms? "If the conclusion of a weaken question is x->y, I should actively search for the answer choice that says x->not y. I should avoid the common trap that says __________".

Thanks in advance!