I thought it was a little weird to throw "presumably cogent" in the answer choice, too, and it didn't seem necessary to include. But I don't believe the answer choice implies anything about the validity of the professor's first argument about the physical environment. Rather, the answer choice is neutral - it's just describing what's going on in the argument.

I interpreted "presumably cogent" as a (needlessly) confusing way of referring to a necessary assumption the professor makes. Specifically, the professor assumes that their first argument makes sense (i.e., their argument is "presumably cogent"), in order to use it as a premise supporting the conclusion of their analogous argument about history books.

Anyway, that's my take, but I could be wrong lol. Hope this helps!

ME TOO ugh

Thank you!! I like this explanation much better

I struggled to understand exactly why E was incorrect for a while as well, but here’s what helped clarify JY’s explanation for me:

E is wrong because of two words: “Any similarity in the DNA of two species must be the result of interbreeding.”

So basically, it’s saying, “100% of the similarity in the DNA of two species is always the result of interbreeding,” which is pretty extreme.

If we try the negation test, we can do it in multiple ways, but here are two: “Any similarity in the DNA of two species doesn’t have to be the result of interbreeding.” or “Not all similarities in the DNA of two species must be the result of interbreeding.”

So when E is negated, the argument doesn’t completely fall apart - the argument is still valid without the assumption that 100% of the similarity in the DNA of two species results from interbreeding.

For example, maybe 99% of the similarity in DNA is the result of interbreeding, and 1% is just from some other random factor. Not all the similarity might be from interbreeding, but we can still reasonably use the comparison of the two DNA’s as a premise in this argument.

Hope this helps!

#feedback it would also be helpful to include the lawgic in the explanation for this one, please!

I'm interested, too! Anyone else graduate in '19?

Yes!

I'm not sure whether there are correct answers where the answer is presented as the contrapositive. But I was also tempted by E until writing out the Lawgic and realizing that it confuses the sufficient and necessary conditions:

"never" is a negate necessary, so I negated "good journalism" and made it the necessary indicator.

/ satisfy curiosity + / info accurate --> / good journalism

contrapositive:

good journalism --> satisfy curiosity or info accurate

This was helpful - thank you!