Literally the only reason why I got this question wrong is because I read and analyzed the wrong portion. Remember, highlight the portion that you're focusing on if you need a reminder to ground yourself.

Completely missed that the question stem said "must be false."

@LSATLOVER Thank you, any advice on how to practice other than more timed drills/practice sections?

This was upsetting and confusing because the phrase "guarantee" made me think that the plants COULD NOT POSSIBLY be disease free, so I ignored (E). In all of my LSAT studying, I have learned to take words literally and not make up assumptions like this.

I understood exactly what I got wrong on the first try and got it right on the Blind Review - I hope this unlocked a new neural pathway for me, lol.

So this question wasn't just about finding an AC that WEAKENS an argument, we just had to find one that DIDN'T SUPPORT the argument.

I think that's why I chose (C) thinking it was an alternate explanation of the cause, when it was actually providing additional comparative evidence for the argument. (D) is the right answer because the info it provides does not matter to the stimulus.