Over the last few years, Country A has suffered a pest infestation which has resulted in huge losses in agricultural yield. Since the infestation began, Country A’s imports have increased. Therefore, Country A will continue to import more than it did before the infestation started, and this will remain so until the infestation ends.
Remember we identified the components of this passage in the introductory article on argument-based passages. Now let us suppose that this passage appeared in your test with the following question-stem and possible answer choices:
Question: Which of the following, if true, most strongly weakens the argument presented in this passage?
A. The economy of Country A has traditionally relied on its agricultural exports.
B. Country A has encountered an electricity shortfall over the last few years, causing most of its tech industry to shut down which in turn has led to an inability for the local industry to meet the country’s growing demand for IT products.
C. The infestations have ravaged the entire countryside; not only are the food crops affected but the industrial crop has also been damaged.
D. A significant proportion of the recent infestation in Country A is caused by the boll weevil pest.
E. Because of the infestation, Country A, a country otherwise self-reliant in diet, has faced major shortages in staple foods in all parts of the country, and the situation does not seem to relent until the pest invasions cease.
Now if you recall the conclusion of the above passage:
Conclusion: Country A will continue to important more than it did before the infestation started, and this will remain so until the infestation ends.
The author reached this conclusion from the premises that Country A has incurred major losses in agricultural yield due to infestation, and that since the infestation began, an increase in imports has already been observed. In other words, the author is trying to argue that since the increase in imports coincides with the losses in yield due to infestation, it must therefore have been caused by and, by extension, end with the infestation itself.
To weaken the argument, we have to select the option that undermines the conclusion that the increase in imports will continue (and end) with the infestation itself. In other words, the right answer choice should suggest (on its own i.e. without requiring outside assumptions) that there may be some other factor(s) involved in increased imports. That way, it will be possible to argue that increased imports may not continue and end with the period of infestation, since it depends on factors other than the infestation. In short, we will have weakened the argument by challenging the assumption on which it stands: that infestation is the only factor contributing to the increase in imports. Let’s evaluate the answer choices to see if any of them weakens the argument.
Answer choice A states that the economy of Country A traditionally relies on agricultural exports. Does it have anything to do with the conclusion that the recent increase in imports was caused by infestation? Not really, it only points to a fact irrelevant to the conclusion of the passage. One may argue that if Country A used to be so self-sufficient in agricultural produce, they must have saved enough for the metaphorical rainy days i.e. there should be no need to increase imports because of the infestation. But that line of reasoning is based on an outside assumption that they indeed saved enough produce to not let them get affected during times of crisis. In any case, this answer choice does not undermine the conclusion on its own.
Answer choice B is correct. It states that an electricity shortfall has also occurred over the last few years, which has dealt a blow to the country’s technology industry. This has led to an inability of the local tech industry to meet local demands. Does it prove that the recent increase in imports was due to the agricultural losses caused by infestation? No, in fact it suggests the opposite by pointing out another possible cause for the increase in imports. In other words, it raises doubts about the conclusion being correct and hence successfully weakens the argument.
Answer choice C only further elaborates the point that country has incurred considerable losses due to infestation by stating that the losses occurred in both food and non-food crops. However, it does not weaken the argument that the infestation is the main cause of increased imports. If anything, it should only serve to bolster that argument (although we have already established in Strengthening the Argument that that too will require an additional assumption).
Answer choice D only specifies one of the pests involved in the infestation. Needless to say, it is irrelevant to the question stem i.e. it does not weaken the causal relationship between the increase in imports and the infestation.
Answer choice E states that infestation has caused serious shortages in food all over the country, that the situation will remain unchanged until the infestation ends and that before the infestation the country used to be self-reliant in food. We have shown in Strengthening the Argument how this makes Option A a great case for strengthening the conclusion. So it is, most definitely, not undermining the argument.