One year, large quantities of the catnip weed bloomed in corn fields

Question

One year, large quantities of the catnip weed bloomed in corn fields located in a region with a large aphid population. Since aphids feed on cornstalks, the fields would normally attract aphids, yet no aphids were found in the fields. Nepetalactone, a chemical produced by the catnip weed, is known to repel several types of insects, including aphids, so it is likely that the nepetalactone from the catnip repelled the aphids.

Which of the following, if true, most strengthens the argument?

A. Nepetalactone is also found in clovers but at concentrations lower than in the catnip weed.
B. Many insect species not repelled by nepetalactone were found in the corn fields throughout the year.
C. By the end of the year, most of the cornstalks in the fields had been killed by fungi transmitted from the catnip.
D. The aphid population of the overall region was much lower during the year in which the catnip weed bloomed than it had been in previous years.
E. Aphids are known to be susceptible to toxins in plants other than the catnip weed, such as larkspurs.

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aditya1818 · Answer

I will use POE

A. Nepetalactone is also found in clovers but at concentrations lower than in the catnip weed.-  Incorrect: So what? does comparison with clovers doing anything?-No. 
B. Many insect species not repelled by nepetalactone were found in the corn fields throughout the year.- Correct: If other insects not repelled by the chemical was found and those repelled where not found indicates it is the chemical which is causing the problem. 
C. By the end of the year, most of the cornstalks in the fields had been killed by fungi transmitted from the catnip.- Incorrect: Cornstalks killed by fungi doesn't help me reach to my conclusion in any way. 
D. The aphid population of the overall region was much lower during the year in which the catnip weed bloomed than it had been in previous years.- Incorrect: This gives a co-relation between them but doesn't bring the chemical into play to strengthen it. 
E. Aphids are known to be susceptible to toxins in plants other than the catnip weed, such as larkspurs.- Incorrect: Aphid is affected by others does not necessarily indicates that chemical is the main cause.

Answering why the option is wrong is a good way of elimination.

temporibusquis · Answer

I don't understand why B and not D. I did not consider B as valid because it states Many, while the passage states that several insects are repelled by N.

Dereno · Answer

Usually, the corn fields in the region attract large number of aphids. But, in that particular year, there were Catnip weeds growing in the Corn feilds. Due to which, the aphids which used to get attracted to the corn fields were found missing that year.

They find out that, Nepetalactone, a chemical produced by the catnip weed was responsible for the peculiar behaviour. This chemical used to repel many insects , including aphids. That’s the most likely reason why aphids were missing in the corn fields this year.

We need to strengthen the argument - Nepetalactone produced by catnip is responsible for the aphids not visible in corn fields.

A. Nepetalactone is also found in clovers but at concentrations lower than in the catnip weed.

This Option is irrelevant, as it makes a comparison of chemical Nepetalactone present in catnip weed and Clovers. Hence, wrong.

B. Many insect species not repelled by nepetalactone were found in the corn fields throughout the year.

Insects which are not repelled by the chemical - Nepetalactone, produced by Catnip weeds were found to be visible in the corn fields throughout the year. This clearly proves that Aphids which used to be found in corn fields are repelled due to Nepetalactone. Hence, correct answer.

C. By the end of the year, most of the cornstalks in the fields had been killed by fungi transmitted from the catnip.

This option brings out a peculiar case, why should the aphids feel worried that they didn’t visit the corn fields, any ways it’s going to be killed by fungi. Hence, Wrong. We are asked to ascertain whether chemical Nepetalactone is the reason for Aphids staying out of corn fields or not.

D. The aphid population of the overall region was much lower during the year in which the catnip weed bloomed than it had been in previous years.

The option brings the context of total aphid population before and after the bloom of Catnip weeds. By mentioning the aphids population has dropped significantly, the question of no aphids in corn fields seems natural. So, the cause of Nepetalactone in repelling aphids from the corn fields seems irrelevant. So, this is actually a good weakening point. Hence, Wrong.

E. Aphids are known to be susceptible to toxins in plants other than the catnip weed, such as larkspurs.

This explains the susceptibility of Aphids to certain toxins. This doesn’t explain the reason behind why Aphids were missing in the corn fields. This option brings a new player into the picture. Hence, wrong.

Option B

arushi118 · Answer

From option B we can say eliminate other reasons which could be the cause of insects being repelled:
The fields were not generally hostile to insects.
The only insects missing were the ones known to be repelled by nepetalactone—i.e., aphids.

Hence, B most directly strengthens the conclusion that nepetalactone from the catnip weed repelled the aphids.

arushi118 · Answer

D is a weakener, and not a strengthener. It gives us another reason - that the aphid population was less in the fields because their overall population was less and not because they were repelled by nepetalactone.

liberopossimus · Answer

I think, for B, the point here is "not repelled" by nepetalactone. This basically says that the presence of insects other than those which are repelled by nepetalactone (unlike aphids) were repelled. Thus strengthening the conclusion that nepetalactone was responsible for repelling aphids.

For D, the lower population of aphids, would basically weaken the conclusion. Since the conclusion here was that nepetalactone was responsible.

pappal · Answer

the only options which attracted my glance relevant to the argument were B and D, rest out of scope.
however B beats D in that, mention of  none aphids found in the field because of the chemical  in the argument, against mention of  just lowering of the population even when the weed bloomed  in the option choice D.
so B

aditya1818 · Answer

temporibusquis

The heart of the argument/stimuli is "   nepetalactone from the catnip repelled the aphids"   and the reasoning to it is   "chemical produced by the catnip weed, is known to repel several types of insects"

Now, forget the conclusion as of now and bring the reasoning as stated above and options together,

With option (D)   The aphid population of the overall region was much lower during the year in which the catnip weed bloomed than it had been in previous years   and reasoning  "chemical produced by the catnip weed, is known to repel several types of insects"  so ask yourself, did the option really reasoned it out strongly that  "   nepetalactone from the catnip repelled the aphids"   . The answer is a big No. Maybe an another reason could have affected that year and so aphid population was less or it might be a co-incidence moreover and that's why I said it that it represents co-relation to me.

Now, do the same for option (B). You'll see option (B) reasons out better with the premise to reach out the conclusion and a mere "severe" and "many" are not to be considered or stressed upon.

I hope my reach out to the question/answering has brought you some good.

ExpertsGlobal5 · Answer

Expert's Global Video Explanation:

https://www.youtube.com/watch?v=lYQ_ps3Rod4

One year, large quantities of the catnip weed bloomed in corn fields

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