Hi I would love to join as well!

So I got this wrong the first round, but I got it during BR because the point of a SA is to make the conclusion 100% valid.

SA's are like an additional premise... so the question you need to ask yourself is what premise added into this stimulus would make the conclusion valid, what AC would make Mr. Kapp wrong?

If you add in D as a premise, we get why this is wrong. If you add any other AC as a premise, we have no clue why what he did was "wrong".