SO COnFUsing. I just think of it like. If theres two options for one thing, thats the necessary immediately off the bat. THe sufficient cant have more than one outcome. :)

*TIP* (Cause I’m not intuitive at all). I try to think of it in terms of language parameters: All + subject + verb + object. The subject is exhaustive and therefore, is the sufficient clause encased by the object. Otherwise. Only + subject + verb + object. The subject is limited in scope. Just because only one group does something, it leaves the possibility that not all in that group do it. Therefore the second clause, is needed to create the conditional parameters. I would start with the subject (or clause being modified by the conditional indicator words). And then consider whether that subject/claim is exhaustive or limited. Hope this helps? This how I think it out :)

I would argue that the stimulus would be logical argument if the conclusion said “is too difficult…or not worth domesticating” but the fact it says “either would…or would not” implies indefinitely into the future which is not certain unless difficulty is constant indefinitely . Answer B is still bad in my opinion, because it says nothing about the future. The fact that the stimulus already says “since those days” covers from past up until present. In addition, “innumerable times” strongly implies often and frequently. Answer B, if right, further requires the assumption that the future difficulty can be predicted based on the block of time between past and present. HMMMM??!? I guess it’s reasonable assumption. BUT y’all mean >:(