I mean look at this question alone, all 5 can weaken it. It’s just a matter of how much. And trust me, they are very capable of creating questions with answer choices where all 5 can weaken (or strengthen) and ask which one most weakens. I passed the CPA exam and this was a very common question type on multiple sections of that exam as well. It is a very common question type and something to look out for on test day. In college we’re used to seeing 1 right AC and 4 wrong but in these exams that can all change so I was just warning people to keep an eye out. If you don’t want to believe then by all means whatever works for you.

But your argument of “only 1 answer choice truly weakens” can’t be true or else the question would just ask “which one weakens the argument”. They specifically add the “most” for a reason, because they know more than one AC does weaken it.

Something I want to point out: This question doesn't ask which of these answer choices weakens the argument. It asks which of these choices most weakens the argument made. That is a massive difference. All 5 answers can weaken the argument, but it asks which of the 5 most weakens it. I haven't seen that pointed out in the videos.