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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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GM genes were found initially in juvenile hybrid salmons.
Disappeared later ----> After 3 years---> No trace of GM genes.

What could be the reason?

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
This option explains why there were traces of GM genes found initially and later due to low survival rates, the hybrid ones weren't able to survive and hence no traces were found.
Correct.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
This contradicts the situation. The GM salmons would survive better in this case.
Incorrect.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
The argument is about the offspring and not the adult GM, which later migrated.
Incorrect.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
Still doesn't explain no trace of GM genes. There could've have been some trace of GM genes in this case.
Incorrect.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
Still they can breed and GM genes can be found.
Incorrect.

ANSWER: A
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The core of the discrepancy is that GM genes were found in the first study but not in the second, three years later, even though GM salmon had interbred with wild salmon. We need an option that explains the disappearance of the GM genes.

Let's evaluate each option:

A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. This option directly explains why the GM genes might disappear from the population. If the hybrid offspring are less likely to survive, then over time, their genes (including the GM genes) would be selected against and decrease in prevalence, potentially disappearing within three years. This strongly helps explain the discrepancy.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. This would suggest that GM salmon (and potentially hybrids) would survive better, which is the opposite of what's needed to explain the disappearance of GM genes.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. While this might explain fewer GM salmon in the river, it doesn't explain the disappearance of the GM genes from the wild river salmon population that had already interbred. The GM genes were already confirmed in juvenile wild salmon in the river.

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. This option talks about wild salmon migration patterns, but it doesn't explain why the GM genes that were already present in juvenile wild salmon would disappear. If anything, it might suggest that some wild salmon carrying GM genes could still be out there, just not sampled. It doesn't explain a disappearance.

E. Fewer than ten adult GM salmon escaped before the facility was closed. While a small number of escapees might mean a lower initial prevalence of GM genes, it doesn't explain their complete disappearance after they were already confirmed to have interbred and produced offspring with GM genes. If they bred at all, and the offspring survived, the genes should still be present.

Conclusion: Option A provides the most direct and logical explanation for the disappearance of the GM genes from the wild salmon population. If the hybrid offspring are less fit, they will be naturally selected against, leading to the reduction and eventual absence of the GM genes.

The final answer is A.
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It is stated that GM salmons escaped from a lab. The impact of this was seen when testing of juvenile salmons showed GM in their genetics. The lab was shutdown and all the remaining GM salmons removed. 3 years after a follow up testing that sampled hundreds of wild salmon found no trace of GM genes.

Option A most likely explains the reason. It means the young salmons previously observed did not survive and thus could not procreate
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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.
That would mean the GM genes died out naturally over time. They showed up early (in baby fish), but those fish didn't live long enough to grow up or reproduce.

B. Natural predators tend to avoid genetically modified salmon because of differences in their taste.
That would mean GM salmon and their genes should survive better, not worse.

C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
But the question is about their offspring, who were already in the rivers (as proven by the first study).

D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
But scientists tested hundreds of fish. If GM genes were still around, they'd likely show up.

E. Fewer than ten adult GM salmon escaped before the facility was closed.
That might explain why there weren't lots of GM genes. But even a few can pass on genes.

Answer A
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Option A is the correct answer.

Let's understand the passage before diving into the options.

So the passage starts by telling us that in a laboratory the researchers have found out that a species of a genetically modified (GM) salmon has escaped an aquaculture facility and interbred with the wild salmon in a local river system. It then tells us that In the first spawning season after the escape, genetic testing of juvenile wild salmon confirmed the presence of GM genes and then the aquacultural facility was shut down and the remaining GM salmon were removed. Then after three years a follow-up study was conducted on hundreds of wild salmon and found no trace of GM genes in them. Now the question asks us to find the reason for this discrepancy in data.

So from here we can conclude that we need to find an answer option which will tell us why the GM genes were not found in the salmon now after three years. Let's check all the options to find the reason for this observation.

Option A: "Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon". This option tells us the survival rate of offspring of GM salmon is lower than the offsprings of two wild salmon which would mean that within these three years all the offspring of GM and wild salmon have died leading the researchers to unable to find the GM genes in the sample. But let's check other options as well before marking this as the correct answer. Selected

Option B: "Natural predators tend to avoid genetically modified salmon because of differences in their taste". This option tells us that the natural predators avoid hunting GM salmon which results in the genes of GM salmon to be still present in some or many salmon. So this option does not help us in finding the reason for the discrepancy. Eliminated

Option C: "Genetically modified salmon are more likely to escape into ocean environments than remain in rivers". It may be true that the GM salmon prefer ocean environments rather than rivers but in the starting of the passage it was mentioned that GM genes were found in the local wild salmon. Just like GM salmon, they might have shared their genes with other wild salmon. So this option also does not give the proper reason for the discrepancy in data. Eliminated

Option D: "Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years". This option tells us that the salmons in the river migrate to distant spawning grounds and return back only in every few years but does not give any information why the sample of hundreds of salmons tested does not contain GM genes as they can wild salmons can go anywhere to spawning and return which would mean that there must be some GM genes available in the present count of wild salmons. Eliminated

Option E: "Fewer than ten adult GM salmon escaped before the facility was closed". This option is irrelevant as we are not concerned how many salmon escaped from the facility because the sample in which GM genes were found might have shared their genes with other wild salmon. So this also does not give the reason for discrepancy. Eliminated

So, after checking all the options we can say Option A gives us the proper reason why the GM genes were not found by the researchers after three 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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A. Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon. Correct. This choice perfectly explains the existing discrepancy
B. Natural predators tend to avoid genetically modified salmon because of differences in their taste. Even if it is true it does not explain what happened
C. Genetically modified salmon are more likely to escape into ocean environments than remain in rivers. Plausible explainer but not exhaustive because more likely is not the same as all
D. Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years. Out of scope
E. Fewer than ten adult GM salmon escaped before the facility was closed. Irrelevant

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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The Discrepancy-
  • First study (right after escape): GM genes were found in juvenile wild salmon.
  • Second study (3 years later): No GM genes found in hundreds of wild salmon.
That’s surprising — if GM genes were introduced once, why are they gone?

Choice A- Offspring of genetically modified and wild salmon had significantly lower survival rates in the river environment than offspring of two wild salmon.
---> If GM genes were present in the first generation but couldn’t persist — so there could be many reasons like due to lower fitness, natural selection, or sterility — and that would perfectly explain why they disappeared over time.

Choice B- Natural predators tend to avoid genetically modified salmon because of differences in their taste.
---> It has Opposite effect than what is stated in the argument.
Choice C- Genetically modified salmon are more likely to escape into ocean environments than remain in rivers.
---> Not relevant to what is stated in the argument. The question is about GM genes in wild salmon & not where GM fish go after escaping.
Choice D- Wild salmon in the river system typically migrate to distant spawning grounds and return only every few years.
---> Irrelevant. This is about wild salmon behavior, not about GM genes or survival.
Choice E- Fewer than ten adult GM salmon escaped before the facility was closed.
---> Insufficient. Even a small number can introduce genes into a population. This doesn’t explain why the GM genes disappeared after being detected.

So, the only option A directly resolves the discrepancy.
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