Provincial public safety experts have recorded a greater number of gen

Hi unverifiedvoracity and mono1,
why D and E cannot be the answer..

PARA - para tells us that amphibians are found to be having a greater genetic mutations. some have given the reason as the proximity of nuclear plants and the radioactive material is passed to stream when this water is used to cool the plant and then released back to water.
However the conclusion is - even though when the plant is closed for maint and the cases go down, radioactive remain fo ra long period and this drop should not have been there so there is some other reason..
we have to weaken it..
D.Different radioactive isotopes can decay at different rates depending on the chemicals present at the time of the decay.
May be true about these isotopes BUT it does not affect our argument.
this in a way can stregthen it..It gives credence that these isotopes do not decay immediately then how does the number go dowm on closing down.. why immediate effect of closing down

E.Genetic mutation in reptiles and mammals that live near the power plant is less common than it is for nearby amphibians.
we are talking of radiations spread through water. this just strengthens the belief that the contamination is spread through water But does strengthen or weaken that there is another cause or it is through these radiayions transmitted through water

Correct choice C
C.The consistent currents of nearby streams could move trace amounts of radiation downstream relatively quickly.
this tells us that the radiations may exist for a long period But they get washed away by the current of water and that is the reason why incidence of contamination goes down..
CORRECT

Provincial public safety experts have recorded a greater number of genetic mutations in amphibians in close proximity to the nuclear power plant in Beltherton. Some theorize that even though the nuclear reactor is firmly sealed, the water used to cool the reactor might contain trace amounts of radiation that is then released into nearby streams. However, there’s likely another cause of the mutations since although the mutations occur less frequently after the power plant closes for maintenance, radiation remains harmful for thousands of years

First opinion : water used to cool the reactor might contain trace amounts of radiation that is then released into nearby streams

Counter Opinion : there’s likely another cause of the mutations. radiation remains harmful for thousands of years.

what assumption lies behind this counter opinion : radiation alone without combination can cause the effect i.e. genetic mutation in amphibians.

what can falsify this assumption. Instances will be such as radiation with other medium can do the same thing.

A.The mechanisms that allow trace amounts of radiation to genetically mutate a life form are not particularly well known. mechanism is not discussed in the passage. so, OFS

B.Some of the mutations were so minor that they were virtually undetectable as the affected amphibians aged. - Strengthens

C.The consistent currents of nearby streams could move trace amounts of radiation downstream relatively quickly.--correct. weakens

D.Different radioactive isotopes can decay at different rates depending on the chemicals present at the time of the decay.-- neither strengthens nor weakens

E.Genetic mutation in reptiles and mammals that live near the power plant is less common than it is for nearby amphibians.--OFS

I think the answer should be option C. My understanding of the problem :

There are two opinions presented here -- One of the author and the other of the expert. Our job is to weaken the stand of the author.

Premise : Amphibians in close proximity have higher instances of genetic mutation.

Expert's stand : Water from the coolant is responsible for genetic mutation, as it contains traces of radiation.

Author's stand : Some other reason behind genetic mutation. The author claims that though the facility closes down , radiation lingers for 1000 years.

Question stem : We need to weaken the author's stand.

Pre-thinking step : How do we counter author's view ? We need to prove that - No it is water which is responsible for genetic mutations. In general , we can weaken such claims by either attacking the conclusion, basis or link(b/w basis and the conclusion). Our answer must hinge on radiation and water.

POE process :

Option A --> Irrelevant
Option B --> Irrelevant
Option C --> Matches our pre-thinking. So what it says is this - water from nuclear plant flows down the stream quite fast and is hence responsible for the damage.
Option D --> Why should we bother about isotopes in the first place ? Out
Option E --> Talks about reptiles and mammals - not of our concern.

This is surely a 700 candidate ! Awaiting OE

Premises:
- There are greater number of mutations in amphibians close to the power plant.
- Experts think that the reason could be coolant water with trace radiation released into the stream.
- Although the mutations occur less frequently after the power plant closes for maintenance (so a contaminant from the nuclear plant while it is working comes across as a more probable cause of mutations) , radiation remains harmful for thousands of years (if it were the radiation released into the water, a few days of closing down the reactor would not decrease mutation since radiation remains harmful for 1000s of years so the water would still be harmful)

Conclusion: There is likely another cause of mutations.

Weaken the argument. So find a reason that makes contaminated water a more likely cause of mutations.

A.The mechanisms that allow trace amounts of radiation to genetically mutate a life form are not particularly well known.
"Not well known" does not strengthen or weaken the conclusion. It doesn't add to the information we possess till now.

B.Some of the mutations were so minor that they were virtually undetectable as the affected amphibians aged.
The level of mutations is irrelevant. We are only worried about the number of mutations.

C.The consistent currents of nearby streams could move trace amounts of radiation downstream relatively quickly.
The harmful water is moved away relatively quickly. This could explain why the mutations occur less frequently after the power plant closes for maintenance. The radiation remains harmful for long but the harmful water is moved away by the stream. So if the plant is closed for maintenance, the mutation level is likely to go down. This reduces the need for a different reason for mutations and does make it more likely that contaminated water is the culprit. The observed phenomena agree with the contaminated water cause.

D.Different radioactive isotopes can decay at different rates depending on the chemicals present at the time of the decay.
First of all, this option is too technical without enough information in the argument. It expects the test taker to understand isotopes and their rate of decay and the relevance of decay (converting radioactive to non-radioactive) etc. Hence, I doubt an official question would have such an option.
Even if I assume that it is understood by everyone, all it says is that different isotopes decay at different rates so some become harmless faster and some slower. Still, we are given that radiation remains harmful for 1000s of years. Hence even if some isotopes decay faster (say a day), there are some that take time. So water does remain harmful for a long time.

E.Genetic mutation in reptiles and mammals that live near the power plant is less common than it is for nearby amphibians.
This makes it likely that the problem is in the water especially if life in the river suffers the most. But what in the water causes it, we can't say. Is it the radiation from nuclear plant, we can't say. The "other cause" could be something else in water. Also, it is possible that it is because of some other differences between "amphibians" and "reptiles and mammals".

Answer (C)

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