it's not a perfect system but it's worked for me in a pinch and worked for me on this question :)

idk if this will help anyone, but something I've found to work on these when I can't understand either the stimulus or the answers is testing to see which of the answers works when it's inserted just before the final sentence. I'm not sure if this makes sense, but a pattern I've noticed with a lot of these questions is that the correct answer works really well in the context of being the second-to-last sentence in the stimulus, so if I'm confused or doubting my answer this has worked for me like 90 percent of the time to check and see what makes the most sense - I think this helps me figure out how the answer fits logically into the stimulus, and adds to the flow of the stimulus to round out the argument :) just sticking this here in case it helps even one person better wrap their head around these because truly Sufficient Assumption is proving to be my personal enemy #1 lol

I don't understand why A is wrong at all :D would someone be able to explain it?

why is this only medium difficult be so fr

On number 4, why is there no chain and why is there no connection between increase and cast? This is what I have:

increase --> mixed

/mixed --> /increase

mixed --> cast

/cast --> /mixed

increase --> mixed --> cast

/cast --> /mixed --> /increase

increase --> herbivicus