V32-17

Question

The level of nitrous oxide in the rural areas surrounding Calcutta is significantly higher than in rural areas near Ahmedabad. Observations show that Cytopots—a bacterium living about two meters below the soil surface—multiply more rapidly in Ahmedabad than in Calcutta. Because nitrous oxide is suspected of inhibiting the bacteria’s growth, an experiment was conducted to test its effects. Two laboratories—one in rural Ahmedabad and one in rural Calcutta—grew the bacteria in a variety of soils under conditions that filtered out environmental nitrous oxide. Nevertheless, Cytopots in the Ahmedabad lab still grew more rapidly than those in Calcutta.
 
Which of the following, if true, would be most important to consider in evaluating the experiment’s outcome?

A. The Calcutta laboratory was situated in an area of the city where nitrous oxide levels were significantly lower than those found elsewhere in the region.
B. In both laboratories, the bacteria grew substantially faster than they did under outdoor conditions nearby.
C. The Ahmedabad laboratory was considerably smaller than the Calcutta facility used in the research.
D. The humidity-control filters employed in the laboratories operated slightly more efficiently in Calcutta than in Ahmedabad.
E. Calcutta’s soil contains inherently higher levels of carbon monoxide than soil in Ahmedabad, and carbon monoxide is another known inhibitor of the bacteria’s growth.

souvik101990 · Answer

Official Solution:

The level of nitrous oxide in the rural areas surrounding Calcutta is significantly higher than in rural areas near Ahmedabad. Observations show that Cytopots—a bacterium living about two meters below the soil surface—multiply more rapidly in Ahmedabad than in Calcutta. Because nitrous oxide is suspected of inhibiting the bacteria’s growth, an experiment was conducted to test its effects. Two laboratories—one in rural Ahmedabad and one in rural Calcutta—grew the bacteria in a variety of soils under conditions that filtered out environmental nitrous oxide. Nevertheless, Cytopots in the Ahmedabad lab still grew more rapidly than those in Calcutta.
 
Which of the following, if true, would be most important to consider in evaluating the experiment’s outcome?

A. The Calcutta laboratory was situated in an area of the city where nitrous oxide levels were significantly lower than those found elsewhere in the region.
B. In both laboratories, the bacteria grew substantially faster than they did under outdoor conditions nearby.
C. The Ahmedabad laboratory was considerably smaller than the Calcutta facility used in the research.
D. The humidity-control filters employed in the laboratories operated slightly more efficiently in Calcutta than in Ahmedabad.
E. Calcutta’s soil contains inherently higher levels of carbon monoxide than soil in Ahmedabad, and carbon monoxide is another known inhibitor of the bacteria’s growth.

A) Incorrect. The experiment already filters out environmental nitrous oxide, so even if this particular lab area has lower N2O levels than typical for Calcutta, it doesn&rsquo;t change the fact that N2O was neutralized in the test conditions. Also, this answer choice does not address why the bacteria still grow more slowly in Calcutta&rsquo;s soil than in Ahmedabad&rsquo;s.

B) Incorrect. This answer choice indicates only that indoor, filtered conditions are better than outdoor conditions for bacterial growth&mdash;something that applies equally to both cities and does not explain the difference between Calcutta and Ahmedabad results, which is the whole point of the experiment.

C) Incorrect. This is irrelevant as we have no evidence or indication that Lab size could in some way explain why bacteria multiply faster.

D) Incorrect. Even if Calcutta&rsquo;s humidity filters are more effective, this fact alone is irrelevant when it comes to slower bacterial growth. If anything, better environmental controls could promote (rather than inhibit) growth. These are not N2O filters by the way.

E) Correct Answer. This is an alternative explanation that helps resolve the paradox. Since we are told that carbon monoxide is another known factor that can inhibit Cytopots, so it can also impact growth and even after filtering out nitrous oxide, Calcutta&rsquo;s soil/environment would still contain this additional inhibitor. This is the best and the only correct answer choice that explains the puzzling outcome of the experiment.

Answer: E

kop18 · Answer

The only issue I find in this question is the "question" it is asking. At the surface level, it is asking us to "evaluate" the stem, however, in my opinion, it should have indicated in some way that it was a "paradox" based question. In that case, the options would have made more sense with the question stem as well, if that can't be tweaked then at least the options must be tweaked to maintain the flow of the question.

There is a little gray area in this question. Can someone help me in case I am missing something?

There is a little gray area in this question. Can someone help me in case I am missing something?

BottomJee · Answer

I think this is a  high-quality  question and I agree with explanation.

Elite097 · Answer

To evaluate the results of the experiment regarding the effect of nitrous oxide on the multiplication of Cytopots bacteria in rural Ahmedabad and Calcutta, it is essential to consider factors that could influence the bacteria's growth apart from nitrous oxide. The correct answer will point to a factor that could potentially confound the results of the experiment.

Let's analyze each option:

A. The laboratory in Calcutta was located in a part of the city where nitrous oxide levels were far lower than is typical for the entire region.

This is not directly relevant since the experiment already filtered out environmental nitrous oxide in the laboratories. The location's nitrous oxide level shouldn't affect the results under controlled conditions.

B. At both the laboratories, the bacteria grew much more rapidly than did those in outdoor conditions near the laboratories.

This indicates that the laboratory conditions were conducive to bacterial growth compared to outdoor conditions, but it does not help explain the differences between the two cities under laboratory conditions.

C. The laboratory in Ahmedabad was much smaller in size than that used for the research in Calcutta.

The size of the laboratory could influence various factors such as temperature regulation, but it doesn't directly explain why the bacteria would grow more rapidly in one location over the other when environmental nitrous oxide is filtered out.

D. The filters used to eliminate nitrous oxide in the laboratories in Calcutta were switched more frequently than those in Ahmedabad.
Potential Impact: This option suggests that the frequency of filter changes might affect the nitrous oxide levels in the laboratories. If Calcutta's filters were switched more frequently, it could mean that nitrous oxide levels were more effectively controlled in Calcutta than in Ahmedabad.
Reasoning: If the filters were more effective in Calcutta, one might expect better growth conditions for the bacteria there. However, this does not directly account for why the bacteria grew more rapidly in Ahmedabad. Instead, it suggests that the filtration system in Calcutta was potentially more robust, which should theoretically benefit bacterial growth if nitrous oxide is a deterrent.

This could be significant. If the filters in Calcutta were more effective or more frequently maintained, it might mean that nitrous oxide was better controlled in Calcutta than in Ahmedabad, potentially affecting the growth conditions differently in each location.

E. The soil in Calcutta is inherently rich in carbon monoxide, another known deterrent in the multiplication of the bacteria.

This is highly relevant. If Calcutta's soil has a higher level of carbon monoxide, it could independently hinder the growth of Cytopots, confounding the results of the experiment and making it appear that nitrous oxide has a different effect than it does.
Conclusion
E is the most important factor to take into account because it introduces another variable (carbon monoxide) that could affect the bacteria's growth. This would need to be controlled for or acknowledged to accurately determine the effect of nitrous oxide on the bacteria's growth.

Answer: E. The soil in Calcutta is inherently rich in carbon monoxide, another known deterrent in the multiplication of the bacteria.

gurdgreen1 · Answer

I think this is a  poor-quality  question and the explanation isn't clear enough, please elaborate. Answer choice E does not say that the soil in Calcutta is richer than in Ahmedabad. It just says that it is rich. This makes it vague whereas common sense would tell you for Answer D that filters changed more frequently are better, therefore the conditions were not equal and thus nitrous oxide was not controlled for properly.

bb · Answer

I like your point about "richer" vs. "rich" and I agree that D could throw off the experiment. I also noticed the explanation in the forum was cut off for some reason. I have updated the E. with richer and rephrased D to be clearly incorrect. I have also added 2 weeks of GMAT Club tests for your help improving this question.

AVMachine · Answer

I don’t quite agree with the solution. "under conditions that filtered environmental nitrous oxide". 
Since, The soil is also part of the environment, and same must be filtered out. How come E make any sense, its presenting conflicting information.

bb · Answer

Hi and thank you for the question.

1. Sure, you can assume that it was also filtered out from the soil but I don't think it matters if it was. 
2. Answer choice E) gives us an external factor that explains the results of the experiment - carbon monoxide. What is the conflict you see about it?

I hope it helps. I am also going to enhance the explanation a bit so check that out as well. 
Thx.
BB.

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