RC question need help.(Confused between B and C)

[RonPurewal]

But I forgot this is a RC question, not CR.

In one sense, you have a point here: This question is not typical of GMAT CR items.

On the other hand, "assumption" always means the same thing, so the same methods still apply.

[NL]

"Negate and see whether the argument is destroyed" is a standard approach to assumption questions. Not sure what is "creative" about it.

Because the “manufacture” guides that you should use this “broom” to clean floors, but you see it can be used to sweep ceilings.

In addition, saying that way could eliminate a possibility that I was stupid (for not knowing how to use it).
Cool!

[RonPurewal]

i don't think that's the issue.
rather, the issue is (as always) that "academic thinking" erases our capacity to think like normal people.

e.g., if i gave you something like this...
Which of these 5 items is essential for your business trips?
(a) item 1
(b) item 2
(c) item 3
(d) item 4
(e) item 5
... i'd bet money that you would immediately think in terms of "negation" (without using that term, of course).
i.e., for each item in turn, you'd think, "could i go on trips WITHOUT this item?", and then you'd pick the item for which the answer was "no".
not because you're a genius (though you may be one--who knows), but simply because that's what "essential" means.
likewise for "necessary" and "assumption".

[RohitM269]

Hi Ron,

Sorry, I still did not understand why B is wrong?

C is talking about "standard of comparison". I thought Standard of Comparison means the highest value and other values will be lesser than that.

As far as the correct answer, there is evidence on a small scale and on a large scale.

On a small scale, look at the sentence in which the bold part actually appears:
Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption
They're explicitly comparing the effect of the changes wrought by humans to that of the MSH eruption.

On a larger scale, the entire passage is about what HUMANS have wrought upon the salmon. It's not about "random stuff that affects the salmon".
If they're going to suddenly start blabbing about a volcano, then that example MUST relate in some way to the changes wrought by humans.
If it were something else"”"”e.g., choice D"”"”then it would just be a random piece of randomness, with no good reason at all to appear in this passage.

[RonPurewal]

Hi Ron,

Sorry, I still did not understand why B is wrong?

the eruption of the volcano was not caused by humans, so B doesn't make sense.

the correct answer absolutely must state that the eruption is the basis of an analogy/comparison with the results of human activity.

[RonPurewal]

C is talking about "standard of comparison". I thought Standard of Comparison means the highest value and other values will be lesser than that.

nope.
"standard of comparison" just means "reference point", or, more basically, "something to which we compare stuff".

[RonPurewal]

^^ e.g.,
me: The average African elephant weighs about 10,000 pounds.
friend: That's such a big number that it means essentially nothing to me.
me: Ok. Well, you weigh about 200 pounds, so the elephant weighs about as much as fifty of you.

here, i'm using my friend's weight as a standard of comparison for the weight of the elephant.
my friend certainly does not weigh more than the elephant, but that's unrelated to the fact that his weight is the standard.

[LaraZ595]

Hi Ron,

Sorry, I still did not understand why B is wrong?

the eruption of the volcano was not caused by humans, so B doesn't make sense.

the correct answer absolutely must state that the eruption is the basis of an analogy/comparison with the results of human activity.

Hi Ron,

Sorry but I'm not convinced by this…yet. I don't think B in any way imply that the eruption is at all caused by human activities (what you seems to be suggesting). Also are people sure that the OA is C instead of B? I am so sure that B is the right answer and I cannot find any official source that states C as OA.

C is wrong because "a standard of comparison against which impact of human activity on the gene flow among salmon populations should be measured". The eruption is a comparison to tell people the extend of human influence, instead of any sort of standards to be measured against…A comparison cannot provide a standard…it seems to be suggesting that all human impact should be measured against the standard set by the impact of the eruption…which just doesn't make sense…\\

Thanks!

B is right. in the context, it says "that the effect would be qualitatively different than"

[RonPurewal]

The eruption is a comparison to tell people the exten[t] of human influence

this is EXACTLY what choice C means.

think about your own words here—in particular, why we would need a comparison to express the blue thing.
there's only one reason why, and that's to use the other half of the comparison as a standard (= a frame of reference).

if we were NOT using a standard for comparison, then we'd just state the blue thing by itself. i.e., we'd just give some direct estimate of the extent of the damage.

again, think about "the elephant weighs 10,000 pounds" (which does NOT compare to a standard) vs. "think of your own size; now multiply that by fifty" (which does).
the stuff in this passage is exactly like the latter, and not at all like the former.

[RonPurewal]

let's simplify choice B:

"indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere"

for this choice, we would need...
... an instance in which humans affected salmon somewhere,
and
... consequences of that instance on salmon somewhere else.

we don't have either of these things.
we don't have the blue thing, because humans do not cause volcanoes to erupt.
we also don't have the red thing, because there is obviously no implication of cause-and-effect between the two instances mentioned in the passage—a volcanic eruption and an anthropogenic disturbance are very clearly two different, unrelated occurrences.

so, choice B is just all kinds of wrong.

[ShashankB122]

Thanks Ron !!
Finding an assumption question explanation was really helpful.
Thanks

[RonPurewal]

you're welcome.