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505-555 Level|   Resolve Paradox|         
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 09:55
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The key question is why genetic testing found GM genes in juvenile wild salmon right after the escape, but no GM genes were detected three years later. The best explanation is that the offspring carrying GM genes didn’t survive well over time, so their genetic traits disappeared from the population. Option A states that offspring of GM and wild salmon had significantly lower survival rates than offspring of two wild salmon, which directly explains why the GM genes vanished from the wild population after several years. The other options don’t explain the disappearance as clearly—B talks about predators avoiding GM salmon, which would likely increase their survival, C says GM salmon escape to the ocean, which doesn’t explain gene disappearance from the river juveniles, D about migration patterns doesn’t explain the genetic disappearance, and E about the small number of escaped salmon doesn’t fully explain why the genes vanished after initially appearing. Therefore, option A best explains the discrepancy.
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:03
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A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. => Ok if there are lower survival rates than can explain why three years later there is no salmon with GM genes lets keep this

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. =>
If predator avoid them then there number should have been greater or equal that means they should have been still present but argument says they are not present after three years. so not the ans

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.=> it says more likely to escape in ocean but then few can still be there in river yet after three years none to be found. so not the ans

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. => if they return every few years then they were able to test when they were there so GM jeans fish should have been there but none to be found. so not the ans

E. Fewer than ten adult GM salmon escaped before the facility was closed. => Ok this does not have any impact even if more than this or less than this escaped there offsprings must have been in numbers. so not the ans

henc Ans A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:08
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B and D kinda provide grounds to contradict the statement,
Though C and E appear correct, they just reduce the presence but not make the traces complete vanish.

A explains why the genes could have vanished as the offsprings didn't survive

Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. CORRECT. If they had lower survival rates, chances are they eventually vanished in 3 years
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste: This would mean that more GM salmons should have survived and therefore should be present.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers: Still doesn't explain why there was no GM genes found, as some could still be present in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years: follow-up study sampled hundreds of wild salmon so it doesn't matter if they migrated to distant grounds
E. Fewer than ten adult GM salmon escaped before the facility was closed: Irrelevant whether only 1 escaped or 5
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:24
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Background: A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system.
Premise: In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed.
Conclusion: Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Why is that after removing all GM salmons, the juvenile wild salmon genetic tests found no traces of GM genes?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
This resolves the paradox. If offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon, then it must be the case that after three years all GM genes wild salmons have died.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
This increases the paradox. If predators avoid them then why are there no juvenile GM genes wild salmons?

C Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
This does not clarifies the question about what happened to juvenile.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
this does not explain why GM genes disappear.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
This does not explain why GM genes disappear.

So A is correct
Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:35
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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
Even though GM genes entered the population, those offspring likely died out.
By the time of the second study, none survived to reproduce → no GM genes left.
Strong explanation for why GM genes disappeared.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
If predators avoid GM salmon, those fish would survive more, not less.
That doesn’t explain why GM genes disappeared.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
Irrelevant: the GM fish already interbred, and we’re concerned about offspring in the river.
This is about adult movement, not gene survival.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
Interesting, but doesn’t explain why GM genes disappeared.
If anything, some fish with GM genes might just be gone temporarily — but the second study found none at all.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
Small number could limit the spread, but we already saw GM genes in juveniles. Doesn’t explain why those genes completely disappeared.

Answer A
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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.- Hence no trace of GM genes
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. - If this were the case, then the GM genes should still have been around
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. - Not relevant.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. - Not relevant
E. Fewer than ten adult GM salmon escaped before the facility was closed. - If this were the case, then the GM genes should still have been around

Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:44
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Quote:
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.
Show more

Premise.
1. GM salmon escaped to river
2. First spawning season, juvenile wild salmon confirmed having GM genes
3. All GM salon in facility removed
4. 3 Years Later, no more GM genes among wild salmons

Need to explain how salmon initially escaped from facility and salmon with GM gene from first season disappear 3 years later.

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. = Make sense. KEEP
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. = If predator avoid, then GM salmon should be more likely to survive. Eliminated
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. = Make sense. KEEP
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. = Even if they migrate elsewhere, the GM salmon can still breed within the river system. Eliminated
E. Fewer than ten adult GM salmon escaped before the facility was closed. = Offsprings can grow exponentially even with 1 salmon escaped. Explanation not strong enough. Eliminated

Between A and C.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
A comparative statement. We have no idea how more likely they are and their actual chance figure. It might be the case that Wild salmon has 1% probability to escape and GM salmon has 2% probability to escape. 2% is very small number and will not signify that significant portion of them are escaping to river.

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
The word 'significantly' here should ring a bell. If they have significantly lower survival rate, then GM salmon will naturally be dead over time after 3 years. Although a comparative statement and we don't know the rate, the word 'significantly' means that it is low enough that can make significant impact.

A is definitely better than C
ANSWER = A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:51
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This was a tough one, at least for me. This is how I approached:

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
  • This gives us a reason to believe that since there was gap of 3 years between the 2 studies, and GM salmon have lower survival rates that wild salmon, there is a possibility that by the time the second study was conducted the GM salmon didn't survive. Keep
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
  • This is irrelevant to the argument. Eliminate
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
  • This also gives a reason to believe that the absence of GM salmon during the second study could be that they moved to an ocean, but since this just talks about a likelihood scenario and nothing concrete like the actual survival rate, this can be eliminated.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
  • Since wild salmon were present in both studies 1 and 2, their migration to and from spawning grounds is not relevant. Elminate
E. Fewer than ten adult GM salmon escaped before the facility was closed.
  • The number of GM salmon that escaped is irrelevant.

A seems to be best choice.
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 10:58
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Question:

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A) This would help . Lower survival rates could lead to them dyeing off over time.
B) This would not help. This would explain higher levels of GM salmon not lower
C) This could help but really doesnt prove that causes anything besides spread of GM.
D) This would not help explain
E) Doesn't explain why it is zero. only helps a small amount.

There are some that slightly help, but the only one that most helps is A

ANSWER: A
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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
Correct, if they have a low survival rate, then it helps to explain the paradox that they might not have survived.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
In this case, the GM population should increase, but it is wrong
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
GM, but what about offspring, with wild salmon, no information why no GM gene

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
Wild salmon is not in the discussion
E. Fewer than ten adult GM salmon escaped before the facility was closed.
ok, but this is not giving any information on why there were no genes of GM or their offspring
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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. Correct. the offsprings couldn't survive to grow in population.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. Further increases the discrepancy.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. What about the GM Wild salmon?
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. Sample collected had wild salmon.
E. Fewer than ten adult GM salmon escaped before the facility was closed. the figure is irrelevant

Ans A
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We're discussing how, theoretically, even if we eliminated the source, the hybrid salmon's offspring would still inherit the genes of these modified salmon. But why, after three years of research, can't we find these genes anymore?

Let's think about it:
- Did they all die off?
- Did they all escape?

Let's look at the options:

A. "GM × wild offspring have significantly lower survival rates in river environments compared to offspring of two wild salmon." This directly states that, even though hybrids were initially produced, carrying the GM gene, they didn't survive past childhood and therefore all died off. That's why these genes aren't seen in the adult sampling three years later. This best explains the difference between the two research results.

B. "Predators usually don't eat GM salmon because of the different taste." This would make GM offspring live better and be easier to find, which is the opposite of "later not seeing GM genes."

C. "GM salmon are more likely to escape to the sea and not stay in the river." This explains why adult GM salmon are rare, but it's referring to the migration of the GM parent generation, not the disappearance of the already detected GM-wild hybrid fry. It's not directly relevant.

D. "Wild salmon usually migrate to distant spawning grounds and only return to the river every few years." This is a methodological issue: if the sampling three years later is mostly of adult salmon, and the hybrid fry from that season take longer to grow up and return, then the later research didn't sample those hybrid offspring. However, the question states that the sampling was "Hundreds of wild salmon," not specifying only mature, returning salmon, and "three years" is quite close to the typical return cycle of most salmon (usually 1–3 years). Compared to A's "low survival rate," this explanation is weaker.

E. "Less than 10 GM salmon escaped before escaping." While the small number of escapes helps, the question already states that "GM genes were detected in the first spawning season," indicating that the number was sufficient to introduce GM genes into the wild population. The number of escapes, "10, doesn't explain why no GM genes were found three years later as directly as "the offspring simply didn't survive."

Conclusion: The best explanation for the difference between the two results is option A.
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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. This is a trap answer, If they has lower survival rates, still some survival is expected. Queston stem says NO TRACE. This won't be the case if the survival is lower


B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.: Out of the context

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.: Trap: If this was the case, then the first season where GM was detected would not be the case.


D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.: Correct answer: if all the salmons after mating has moved to a distant remote location, then the presence of GM breeds will be zero


E. Fewer than ten adult GM salmon escaped before the facility was closed.: Irrelevant
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 11:20
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Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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A research team discovered that GM Salmon has escaped from aquaculture facility and interbred with wild salmon species found in local river system.

After the first spawning season, they found that the juveniles of Wild salmon contained GM genes. This GM genes in wild salmon must have been due to the interbreeding of GM Salmons.

The researchers immediately closed the aquaculture facility, and made sure that the GM salmon species are removed from the area. Three years later, the researchers take a sample of 100 species of Wild salmon and were surprised to see NO traces of GM Salmon species in the river body.

With GM salmon genes initially present , but after three years there is no traces of GM Salmon. So, something must have happened in this three years and would have led to the extinction of GM salmon species.

There might be many reasons for the low trace levels of GM Salmon -

May be , the survival rate of GM salmon species is very low, that they hardly escape the juvenile stage.

OR

there can be specific predator species which feed on GM salmon and this would have led to the extinction of the species

OR some infection would have caused the mass extinction of GM salmon.

Let’s look into the options :

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.

This is the CORRECT answer. Which aligns with our prethinking. This option clearly explains what caused the decline in population of GM Salmon fish.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.

If natural predators avoid GM salmon, the populations would have grown significantly, not diminished. Hence, eliminate.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.

This explains a probability ( more likely) which may or may not occur. Hence, eliminating it.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.

If wild salmon has migrated to distance spawning ground and return back after few years. Few years is not quantifiable, moreover, if wild salmon migrated, then the GM species population should have remained same or increased. But, there is an extinction which cannot be explained by this option. Eliminate it.

E. Fewer than ten adult GM salmon escaped before the facility was closed.

If they have escaped, they must have survived alteast by a fraction. Hence, eliminating it.

Option A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 11:26
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Question type: " Resolve the paradox"

Best way to solve is take choices as true no matter what and eliminate "out of scope"

Premise: GM salmon escaped, interbred with wild salmon
Fact 1: genetic testing of juvenile wild salmon -> GM genes
Fact 2: 3 year later, genetic testing of wild salmon - no trace of GM.

A. mix bred offspring -> lower survival rates in river than offspring of two wild. -> maybe becuase of this no mix bred survived and there are no traces of GM genes now in wild.
(KEEP IT)
B. Natural predators-> avoid GM -> Opposite of this would have been helpful to explain (ELIMINATE)
C. GM likely to escape to ocean environments -> 1. Likely to escape not all escape. 2. There was mix bred 3 years ago. doesn't explain "no trace" (ELIMINATE)
D. Talking about wild salmon - Irrelevant "ELIMINATE"
E. No info given on relevance of No of GM salmon escaped. out of scope "ELIMINATE"


A is the answer

Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 11:49
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Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.

We can keep this option because if the offsprings don't survive we won't expect to find the traces of GM genes 3 years later.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.

This weakens. We can eliminate B.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.

Option A is better to explain the discrepancy. We can eliminate C.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.

Irrelevant to the argument and finding the discrepancy. Eliminate D.

E. Fewer than ten adult GM salmon escaped before the facility was closed.

Similar to D, the information is irrelevant. We can eliminate E.

Option A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 11:57
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The answer seems to be A.

GM modified offspring have low survival rates, hence they were not found after 3 years.
Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 12:06
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I choose A and my reasoning is as follows:
A - If the survival rates were significantly lower maybe their population declined and disappeared over time.
B - If they were predated lesser then their population should've been higher
C - Makes sense but I don't know where the sample was taken from. Requires the assumption that my sample is not representative.
D - Don't know the definition of few years hence ruled out
E - Still doesn't explain why they can't be found today. 10 maybe have bred 1000 times.

Bunuel
A research team discovered that a species of genetically modified (GM) salmon had escaped from a nearby aquaculture facility and interbred with wild salmon in a local river system. In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes. The facility was then shut down and all remaining GM salmon were removed. Three years later, a follow-up study that sampled hundreds of wild salmon found no trace of GM genes.

Which of the following, if true, most helps to explain the discrepancy between the two studies?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
E. Fewer than ten adult GM salmon escaped before the facility was closed.

 


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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 12:08
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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
  • This directly explains why the GM genes disappeared, the hybrid offspring likely died out before reaching adulthood. So by the time the follow-up study was done, none were left to detect.
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
  • This would suggest more GM genes should be found, opposite of what happened. Incorrect.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
  • The escape of adults doesn’t explain why juvenile GM hybrids disappeared 3 years later. Incorrect.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
  • This suggests some salmon may have been absent during the follow-up study, but that wouldn’t eliminate GM genes from all of them. Incorrect .
E. Fewer than ten adult GM salmon escaped before the facility was closed.
  • That explains how few escaped, but not why the genes disappeared after showing up in the first study. Irrelevant.
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