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505-555 (Easy)|   Resolve Paradox|         
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 12:16
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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.
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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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. --> This explains why none of the GM genes were found Correct
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. --> This would actually make GM salmon more likely to survive
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. --> This doesn’t explain their disappearance.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. --> we are talking about a local river system
E. Fewer than ten adult GM salmon escaped before the facility was closed. --> we know GM genes were already found in juveniles, so at least one escaped and bred.
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 12:25
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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.
If the hybrid offspring (with GM genes) don't survive well, they would die off before the second study was conducted three years later. This would directly explain why no GM genes were found in the later study.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
This would suggest GM salmon (or hybrids) might have higher survival rates, or at least not lower, due to reduced predation. This would make it less likely for the GM genes to disappear, so it doesn't explain the discrepancy.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
Explains why the adult GM salmon might not be in the river, but it doesn't explain why the juvenile wild salmon initially found with GM genes (which presumably grew up in the river) disappeared from the gene pool after three years.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
If the salmon migrate and return every few years, the three-year gap might mean the same generation of hybrid salmon wasn't sampled, or that the current population in the river is a different group. However, the initial study found GM genes in juvenile wild salmon in the local river system. If these juveniles don't survive or reproduce, or if the GM gene itself causes a disadvantage over a few generations, then the genes could disappear.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
While this might suggest the initial impact was small, the first study did confirm the presence of GM genes in juveniles. So, even a small number of escapees managed to interbreed.

Regards,
Lucas

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, 12:31
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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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True : Option A –
Offspring of GM and wild salmon were weaker.
They had lower survival rates in the river.
So their genes naturally disappeared over time.

False: Option B:
Predators avoided GM salmon because of taste.
This would help GM salmon survive longer.
So it can’t explain why GM genes vanished.

False: Option C:
Some GM salmon escaped into the ocean.
But GM genes were already seen in baby wild salmon.
So escape doesn't explain their later disappearance.

False: Option D:
Wild salmon migrate and return every few years.
But the study sampled many salmon after 3 years.
Migration doesn’t explain why no GM genes were found.

False: Option E:
Only a few GM salmon escaped the facility.
But even a few can spread genes through mating.
So small number doesn’t explain gene disappearance

Hence ANSWER IS OPTION A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 13:03
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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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We have to resolve the paradox in this question.

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

This information helps resolve the discrepancy. The extra information tells us the three year later study couldn't find trace of GM genes - because the offsprings didn't survive. Hence, we can keep this.

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

This option deepens the paradox. The GM fishes were not eaten. We can eliminate B.

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

The information says that they are like to escape, not that they will escape. Hence, we can eliminate C.

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

Out of scope. Eliminate D.

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

The information is not relevant. We are trying to resolve the paradox and this information has nothing to do with it.

Option A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 14:12
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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 the right answer. It properly explains why there were GM genes in the first spawning, but there are no more after 3 years.

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

This does not explain why there are no GMs now; if anything, it suggests there should be more GMs now because they don't have predators.

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

This could explain why there are fewer GMs in the river now, but it doesn't explain why there are none.

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

This does not explain why the GMs disappeared. If there were GMs in the river before, and they don't migrate, where are they?

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

This could suggest that GMs were not enough to breed with wild salmon. But we already know that happened despite the small number of GMs. We want to know why they disappeared.


The answer is A.
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 is a very good answer which would bridge the gap between why during the first spawning season presence of GM genes was found and why during the testing three years later found no trace of GM genes. The other options discuss conjectures which can seem to be far fetched.
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, 14:43
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Ans: A

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?
Why were there 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.
If the offspring did not survive, then there was no fish to carry the GM gene further down the line. This would explain no GM gene after 3 years.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
If they tend to avoid GM fish then the population could have been increasing for GM gene salmon and traces would have been there.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
GM fish would escape, but as their offspring are already in the river, then GM gene shouldn't disappear.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
We are concerned about the GM fish and particularly their offspring for GM genes.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
#of GM Salmon escaped from the facility is not the point of discussion. and doesn't help understanding the discrepancy.
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 15:36
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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?

Ok. So, we can see that the GM salmons could have an offspring. After a few "generations" no more GM genes were found. We can have some options: (i) this animals could not reproduce effectively, (ii) this animals are more vulnerable than wild ones, (iii) this GM salmons are not really attractive to wild peers (but it would have a hard time because, in a first moment, they could reproduce), (iv) they can have more risk of fatal deseases/mutations, and so on. Let's analyze 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.
Ok, this option looks like a good explanation. Let's keep this answer choice and analyze the next ones.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
This does not help to explain. Actually, this would let easier to GM salmons to reproduce and growth in number. Wrong option.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
This option looks like out of scope. Wrong option.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
This does not help to explain. Doesn't say nothing about GM salmons. Wrong option.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
This does not help explain the situation. If that was the argument, why was it "easily" detected at first, but not in the following cases? There would be at least the same chance of detection if no other factors were involved. Wrong option.

Answer = A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 15:50
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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 right away seems like a very sound explanation for the discrepancy: if the facility was closed, rendering the possibility of more GM salmon entering the river obsolete, then a rational explanation for why the genes are currently absent from the river would be if GM had significantly lower survival rates in a wild habitat and therefore were not naturally selected and did not survive without any further introduction of the gene.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. --> doesn't reconcile discrepancy; adds to it if anything. If predators avoid GM salmon, why are their genes not present?

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. --> Okay, being more likely to escape doesn't necessitate escape, nor does it mean that all of the GM fish that were exposed to the gene pool did escape; doesn't resolve discrepancy enough; too much ambiguity.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. -- irrelevant as to why GM genes are not appearing in the gene pool

E. Fewer than ten adult GM salmon escaped before the facility was closed. --> okay, is fewer than 10 insufficient to affect the gene pool? do we know that with certainty; seems like outside knowledge if we do.

correct answer: A
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, 15:55
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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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In that case, we are searching for anything that gives us any reasoning to build up on the fact, that wild salmon with GM salmon does not work together very well.
A) hold, because that is exactly what we are looking for.
B) Would be a pro, Out
C) Light con, but we are talking about the GMs, not the interbred with the wild ones.
D) not relevant
E) Light con, not relevant

Therefore, we go with A)
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 16:44
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Lets check the options which best explains why GM genes were found first ,but not found three years later

Option A:
Offspring of GM and wild salmon had significantly lower survival rates than offspring of two wild salmon.
GM offspring were initially present (found in first study),But over time, died off more than pure wild salmon, So after 3 years: no GM genes left.
This helps resolve the discrepancy. (This directly explains it)

Option B:Natural predators avoid GM salmon because of taste differences.
This would mean GM salmon survive more, not less. So GM genes would still be found in the second study.

Option C: GM salmon tend to escape into oceans rather than stay in rivers.
That talks about adult salmon leaving rivers. But the GM genes were already in juvenile wild fish. Doesn't explain why those genes disappeared.

Option D:Wild salmon migrate far and return only every few years.
Doesn't explain why GM genes disappeared. Migration would just spread genes, not remove them.

Option E: Fewer than 10 GM salmon escaped.
Even 1 GM salmon can pass genes to many offspring. So this doesn't explain why GM genes disappeared after being found.

Option A Correct answer
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 16:58
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A is the only option that directly accounts for why GM genes were present initially (due to interbreeding) but disappeared later (because hybrid offspring had low survival rates).

ans is A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 18:29
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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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So, B talks about predators we dont know if their are any. C talks about ocean, which is also out of context of passage. D talks about migrating, but passage does not clearly says if their are any other migration grounds near which is also false. Lastly, E tells a fixed number and we are not sure if that was true so this is also false.

Finally we are left with A, and if we consider A then it clearly explains why no gene of GM modified salmon was found as they find it difficult to survive in river.
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 19:03
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The correct answer is (A)

The question provides information that juvenile salmon had GM genes and therefore the interbreeding occurred. Then one must go through the answer choices to see which one provides more evidence for a successful removal of the GM genes and explains why it worked.

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
(If true, this feature of GM offspring would help prevent future surviving GM salmon in addition to the removal of GM juveniles. Therefore it explains why it worked and is the correct answer.)

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
(If true, this would actually validate an increase in GM salmon as predators would avoid them)

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
(This answer if true mentions "more likely" but it leaves it open for some GM salmon to remain and to show up in future studies, therefore not fully eliminating the risk and reinforcing the study)

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
(If true, this would mean some GM salmon would have shown up in the study that happened after a few years.)

E. Fewer than ten adult GM salmon escaped before the facility was closed.
(This would mean GM salmon offspring or these adult salmon should have been found in the study three years later but none were found)
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 19:10
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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 the offspring of two wild salmon.
1. This shows that the offspring of two wild salmon have greater chances of survival in the river environment. This may influence Simon's preference for interbreeding. Let's analyze the other. Keep

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

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
This can be the case in A, and also, all have escaped to the ocean seems a little off.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
If they return, then the chances of zero GM are very unlikely.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
This doesn't do anything at all.

Out of A, C and D, A seems the best answer.
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 19:37
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A. Acording to evolution, that's the reason of worse genes (for surviving in this case) to go extinct. CORRECT.
B. If this was relevant, they woul have eaten the first escaped salmons, more than the offspring.
C. First gen should've escaped too, then.
D. No info about GM, doesn't help.
E. Might mean that the population has a high probability of disappering, but the argument is way weaker than A.

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, 19:44
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Initial Study: GM genes were found in juvenile wild salmon after the escape and interbreeding.
Second Study (3 years later): Follow-up study found no trace of GM genes.

We are asked to resolve or provide explanation for this apparent discrepancy.

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. This choice could explain the discrepancy. If the off-springs of GM salmon and wild salmon are less likely to survive, then it’s possible that they die before adulthood or few or even none of them reaches maturity, leading to gene being eliminated from the pool naturally. Keep.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. If this is true then GM Salmon are more likely to survive. Doesn’t help. Incorrect.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. Irrelevant. GM Salmon already interbred. Where they disappeared later is irrelevant to the explanation. Incorrect.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. Okay! if this is true, we may find few offsprings in the pond because of less interbreeding, but they won’t disappear entirely. Incorrect.

E. Fewer than ten adult GM salmon escaped before the facility was closed. Irrelevant. Do we have the total of how many adult GM fishes were there in total? And what about their offsprings? Doesn’t help explain the discrepancy. Incorrect.

Option A.

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, 19:54
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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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We are looking at the discrepancy between the two studies.

May be some factor contributed to these results, We need to find that out.



A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. Hmm, This could be possible, Bcs of this the last study showd no GMs..
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. Oppsite, Then the GMs should increase.
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. Hmm possible, But there should be some GM left.
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. Irrelavant, Won't help.
E. Fewer than ten adult GM salmon escaped before the facility was closed. Irrelavant.

IMO A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 19:58
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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 GM genes were present initially (from the first spawning) but not later (hybrids didn't survive well). CORRECT

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
If predators avoid GM salmon, they might have a survival advantage, meaning GM genes should persist or even increase. This doesn't explain their disappearance.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
If GM salmon preferred oceans, they might leave the river, but the initial interbreeding happened in the river, and the first study detected GM genes in river juveniles.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
If wild salmon migrate and return every few years, maybe the GM hybrids were part of a group that hadn't returned yet during the follow-up study. But the study sampled "hundreds" over three years, so it's unclear why none would have GM genes unless the hybrids didn't return at all.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
Only a few GM salmon escaped, so the initial interbreeding might have been limited. But the first study did detect GM genes, and even a few can leave traces. This doesn't explain why genes disappeared later.

IMO A
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GMAT Club Olympics 2025 (Day 6): A research team discovered that 07 Jul 2025, 20:45
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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.


The passage explains that some of the Genetically modified Salmons have left the facility and has interbred with wild salmon in the local river bed system and in the first spawning juvenile salmon has been found with GM genes and in view of that complete centre was shut down and all remaining GM salmon were removed. However, after 3 years when follow up study was done no trace of GM salmon gene was found.

Option A clearly explains this discrepancy as offspring of genetically modified salmon has lower survival rate and therefore due to no future GM salmon in the riverbed system has led to extinction of GM slamon genes.

Lets analyze other option as well:

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
This will result in more GM salmon genes if hold true . so eliminate
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
No mention of ocean out of scope. Eliminate
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
But then again other salmon will be present and genes will be found. so eliminate
E. Fewer than ten adult GM salmon escaped before the facility was closed.
Even one GM salmon can increase its population through interbreeding. Eliminate

Correct answer should be A
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