Critical Reasoning

spetznaz wrote:@moumi2013 , the answer is B , experts please enlighten !

Hi Spetznaz,

Here are my two cents. I'll try to apply the 3-step e-GMAT approach, which consists of passage analysis, pre-thinking and lastly, option statement analysis. I hope it help!

Passage Analysis

Plantings of cotton bioengineered to produce its own insecticide against bollworms, a major cause of crop failure, sustained little bollworm damage until this year. - In this part, the author gives us some information about a type of cotton that has been engineered to create insecticide. This insecticide protects the cotton plant against bollworms. Bollworms are a significant reason for the failure of the crop. Such bioengineered cotton plants did not receive much damage from bollworms in the past, but the situation has changed this year.

This year the plantings are being seriously damaged by bollworms. - In this part, the author says that unlike previous years, this year the cotton plants have received a significant amount of damage from bollworms.

Bollworms, however, are not necessarily developing resistance to the cotton's insecticide - Here, the author dismisses a possible explanation for why the cotton crop has been damaged by bollworms. The author says that the damage to the cotton crop does not necessarily show that bollworms have become immune to the insecticide that is produced by the cotton plants.

Bollworms breed on corn, and last year more corn than usual was planted throughout cotton growing regions. - Next, the author states that bollworms breed on corn. This means that they feed on corn and multiply. This part also states that last year, the amount of corn planted in regions where cotton is also planted was greater than usual.

So it is likely that the cotton is simply being overwhelmed by corn-bred bollworms. - The author concludes that the actual reason that the cotton crop was damaged by bollworms is that the number of bollworms increased significantly. So, the author believes that the reason that the cotton was damaged is not that the bollworm has developed resistance to the insecticide produced by the cotton plants, but that the number of bollworms in cotton-growing areas has increased to an overwhelming number because the corn that bollworms breed on has been planted in amounts that are greater than usual.


Prethinking

In evaluating the argument, which of the following would it be most useful to establish?

The question stem asks us to evaluate the given argument. In the argument, the author first describes a situation. Cotton plants bioengineered to ward off bollworms have received a lot of damage from bollworms this year. Then, the author dismisses a possible cause for the situation by saying that it is not necessarily true that bollworms have developed resistance to the insecticide produced by the cotton plants. Instead, the author says that the reason is probably that the number of bollworms in cotton-growing regions has significantly increased. This is because the amount of corn grown in the same areas has increased, leading to a likely increase in the number of bollworms.

So, to evaluate the argument, we need an option that will either weaken or strengthen the conclusion that an increase in the number of bollworms is the probable reason that the cotton plants have suffered damage from bollworms this year.

Let's pre-think some scenarios in which this conclusion can be assessed. For example, let's say that the corn crops have been treated with a pesticide that kills bollworms. In such a case, even though the amount of corn planted has increased, the number of bollworms may not have increased. So, the author's conclusion is weakened. So, one possible correct evaluate option could be "whether the corn planted around cotton-growing areas was treated with a pesticide which could have prevented the growth of bollworms?" If the answer to this question is yes, then the author's argument is greatly weakened. On the other hand, if the answer to this question is No, then the author's argument is strengthened.

Alternatively, let's say there is another crop that grows in the same region as cotton, such as wheat, that is also damaged by bollworms. If the damage caused by bollworms to the wheat crop has also increased significantly this year, this could mean that an increase in the number of bollworms could be the reason for the increase in damage. In such a case, the author's conclusion would be strengthened. In this case, a possible correct evaluate option would be "Whether other plants, which are also affected similarly by bollworms, in the cotton growing areas were also damaged more?"

With this prethinking in mind, let's examine the answer choices.

Option Statement Analysis

A. Whether corn could be bioengineered to produce the insecticide - This choice is incorrect. It talks about a possible solution to the problem of bollworms causing damage to crops. But it does not give any information about what could be the cause of the current increase in damage caused by the bollworms to the cotton crop.

B. Whether plantings of cotton that does not produce the insecticide are suffering unusually extensive damage from bollworms this year - This is the correct answer.

If the answer to this question is Yes, this means that the non-bioengineered cotton plants also suffered a significant increase in damage this year. It means that the "increase in damage" was not specific to only bioengineered plants. This, therefore, strengthens the author's conclusion that an increase in the number of bollworms and not resistance to insecticide likely caused the increase in damage.

Alternatively, let's say that the answer to the question posed by this option is 'no': that is, that non-bioengineered crops did not suffer much more damage from bollworms this year than they normally do. It means that the "increase in damage" was actually specific to only bioengineered plants. Since the damage was specific to bioengineered plants, it indicates that resistance to insecticide (which these bioengineered plants produced) was the reason for damage to cotton plants. In this case, the author's conclusion is weakened.

So, this choice fulfills both extremes of the variance test and is the correct answer.

C. Whether other crops that have been bioengineered to produce their own insecticide successfully resist the pests against which the insecticide was to protect them - This choice is incorrect.

The success of bioengineering in crops other than cotton is not relevant to evaluating the argument. Also, the argument already states that the cotton crops were not damaged much till last year. This means that bioengineering actually worked. So, this option which seems to evaluate the success of the bioengineering process does not help us in the current situation.

D. Whether plantings of bioengineered cotton are frequently damaged by insect pests other than bollworms - This choice is incorrect.

The passage is concerned only with damage caused by bollworms, and not by any other kinds of pests. Whether bioengineered cotton is frequently attacked by pests does not help us to evaluate the author's conclusion about the reason for the increased damage by bollworms to bioengineered cotton crops.

E. Whether there are insecticides that can be used against bollworms that have developed resistance to the insecticide produced by the bioengineered cotton - This choice is incorrect.

Like option A, it talks about a possible solution to the problem of bollworms causing damage to genetically-modified cotton plants. However, this does not give us any information about what could have caused the increased bollworm damage to bioengineered cotton this year.

I hope it help!

Please feel free to let me know if you have any doubts.

Thanks,
Chiranjeev