I find this q very frustrating, but I've been trying to understand where the test makers were coming from (looking at this q + other similar ones) and have gotten to the following understanding:

Steps for NA assumption q:

1. Identify the conclusion (C) and support (S).

2. Roughly identify the gap/weak point between C and S.

3. Go through each answer choice -- which one is required for the argument to hold?

More on step 3 (where the nuance comes in):

Step 3 is where I've gotten tripped up. A straightforward reading of "which one is required for the argument to hold?" = "If the assumption is false then the argument does not hold." i.e. negate the answer choice, and check if the argument is destroyed.

I think the reason this q is so tricky is it's a case where "if the assumption is false then the argument is severely weakened (but not destroyed)" seems to be the correct answer.

So, applied to this q:

C: Govt mandated protection in pretty places can help those places' economies overall, even if they hurt some local industries.

S: Ppl prefer to live in pretty places.

S: Pretty places tend to experience population growth, which encourages businesses to come in.

Rough gaps:

• the pretty places wouldn't be pretty w/o govt mandated protection

• the influx in new residents that pretty places tend to experience is because ppl want to live in pretty places.

• the positive impact of new businesses coming in outweighs the negative impact of some older industries being harmed.

Answer choices:

A. No, this weakens the argument.

B. Negated: "The economies of most regions are based primarily on local industries harmed by govt protections."

This doesn't 'severely weaken' the argument -- the net impact on the economy could well be positive if the new businesses displace the local industries, even if the region's economy is primarily based on local industries now. The argument is based on new businesses coming in, not on local industries being protected from harm.

C. Negated: "If governmentally mandated protection helps a region's economy, it does not do so primarily via encouraging ppl to move to that region.

There could well be another avenue through which govt protection helps the economy, and it could still hold that population growth is itself enough to help the regions' economy overall as the argument says.

D. Irrelevant (comparing to voluntary environmental protection, which the argument doesn't mention at all).

E. Negated: "A factor harmful to some older local industries necessarily must discourage other businesses from relocating to that region.

In this case, the factor is govt mandated protection. If it harms older local industries AND discourages other businesses from relocating, the argument is severely weakened--I can think of ways the argument could still hold, but this AC is the one that it most clearly depends on.

@JoelKeenan I think there's a case that it's possible for E to not be true and the net effect of government mandated protection to help the economy overall.

"A factor harmful to some older local industries in a region MUST discourage other businesses from relocating to that region"

applying to this case:

Government mandated protection discourages businesses from relocating to that region (in some ways, say because it causes more red tape). Government mandated protection also encourages businesses to relocate to that region (in some ways, via population growth as the stim explicitly says).

So the net effect of the factor (government mandated protection) on the economy depends on which impact is stronger.

[Note if you insert "net" into the AC, or think that "net" is implicit in the argument, then I don't think this reasoning holds]

@julielamberth thank you that’s helpful! For what it’s worth, I’ve noticed two main patterns — (1) somewhat “silly” mistakes where I don’t read the ACs closely enough but will get it on blind review— the “jumping on an answer too quickly” that you mention and (2) ones where I narrow it down to two answers and really struggle to understand why the right one is right, even with unlimited time — slightly more common on RC than LR questions for me. I’m more concerned about (2) because I’m less sure how to tackle it on my own plus I worry that I won’t get enough reps at those types of really tricky Qs if I just focus on drilling full exams.

I don't like this question. I was down to AC C and AC E, and had problems with each of them.

AC C states that "one explanation of what mirrors do reveals the traditional tendency of physicists". the text states "motivated in part by the traditional desire in science" I think the jump from science to physicists is a pretty big assumption (presumably it could be traditional in science, but for some reason a large contingent of physicists could not ascribe. Particularly since in this passage "[physicists'] answer" to the question of what mirrors do is the field-of-sight explanation, which doesn't separate the observer from the observed.)

AC E states that considering objects in mirrors to be "mental constructs" (front-to-back) "interferes with an accurate understanding of how primary perceptions function." The text states that "we are accustomed to dealing with our mental constructs of objects rather than with the primary sense perceptions on which those constructs are based."

I think it's a bridge too far to say that the author would think viewing objects in mirrors as mental constructs means that you can't accurately understand how primary perceptions function. BUT I think the author would agree that it probably doesn't help one's understanding of primary perceptions and could reasonably introduce confusion.

I guess it comes down to whether potentially causing confusion (which even that the author doesn't say explicitly) = interference.

Probably it doesn't, but I'm not convinced that's a bigger assumption than the one AC C requires.

@Kevin_Lin right -- so my thinking is even if you agree with lebronfan's reasoning (and I do), given that the q is asking for a necessary assumption, the better answer is one that is insufficient but likely necessary (argument can't be true if it's false) versus one that is sufficient and likely not necessary. Do you agree?

@Kevin_Lin My understanding is very close to lebronfan's. In my view, AC E is not sufficient (because the stimulus does not give evidence that talk psych help given on talk shows is unlikely to be of high quality -- for the reasons lebronfan articulated). I think AC E is likely necessary, essentially because it sets a lower bar than C (it's really tough to imagine a world where C is true and E is false, although you could probably tie yourself in knots to get there somehow).

@ArdaschirArguelles

You say in passage B that "brain size increases AND bipedality causes the birth canal to narrow" but the actual phrasing from the passage is "In the course of hominid evolution, brain size increased rapidly. Contemporaneously, the increase in bipedality caused the birth canal to narrow." Isn't this very clearly saying that brain size increases and at the same time bipedality happens; and bipedality (NOT bipedality AND brain size increasing) --> earlier birth --> more helpless --> more maternal care needed.

I don't think the passage clearly establishes a partial causal relationship between the two.