For anyone who didn't dismiss A, I hope this helps: The stimulus basically cautions against watching music videos as a method to get a grasp of 70s music because cutting-edge musicians (who performed synth pop and punk rock) were the primary makers of music videos. C cautions against using the method of CD format to judge publishing trends because computer game publishers were the primary users of CD format. That parallels the stimulus.

A fails to do this because it's use of the word never is final. We'll never have an unbiased, accurate view of pre printing press. However, both the stimulus and C imply there are alternative means (not music videos, not CDs) to avoid forming a wrong understanding of the trend they're interested in (70s tunes, publishing trends).

I hope I can help:

When I saw "cannot", I immediately put /SAS after the arrow: → /SAS

Then, like you, I noticed "unless." So, I put /AAF in front of the arrow. The premise became: /AAF → /SAS

However, I didn't like the negation in front of both, so I found the contrapositive: /AAF → /SAS became: SAS → AAF

I think this IS what the video did, but didn't slow it down or break it up like I did. The video highlights both cannot and unless, so it knew the sufficient followed unless (negate it) and the necessary followed cannot (negated), but chose right away to flip and negate those. Seems like an understanding that speeds up with practice.

Please give feedback if this is an incorrect interpretation of the video!