Hi OneSeventy2019,
Thanks for the question. Just a forum tip: I recommend explaining why you chose a particular incorrect answer because if I guess why the incorrect answer appealed to you, I could be wrong and confuse you more.
Fortunately, you shared your pre-phrase, so I'll start there: "someone does something, something is affected, therefore the someone must have intended the effect".
It's pretty good, though I would change it to include that the action itself was done intentionally. So, in your words, it is now:
"someone does something
intentionally, something is affected, therefore the someone must have intended the effect"
Now we can compare it to C:
(1) Cheryl denigrates the wine = "someone does something"? Yep, so far, so good.
(2) Her sister picked the wine = "something is affected"? Eh, sure, if Cheryl's sister heard the criticism.
(3) Cheryl indirectly denigrated sister = "intended the effect"?
Nope! That doesn't match.
Answer choice C says nothing about her intending to do it. In fact, the fact that she "may not have realized it" suggests she DID NOT intend to denigrate her sister! So, that doesn't match up.
Remember, if your prephrase turns out to be too general, make it more specific and then take another go at the answer choices.
Good luck!