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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 11:53
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Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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Official's reasoning : Stricter vehicle standard have been effective in reducing the overall air pollution

We have weaken. One common pattern is to find an alternate cause.

A. Incorrect: Not related. We are told that the particulate pollution increase and this statement doesn't throw any light on that. We can eliminate A.

B. Incorrect: Provides an information which doesn't provide any meaningful data to weaken the conclusion.

C. Correct: This provides an alternate reason. The reduce of pollution is not because of stricter standard but due to reclassification.

D. Incorrect: Doesn't help in anyway. If the traffic fell in one region and increase in another region that doesn't help weaken anything.

E. Incorrect: Irrelevant to the conclusion of the argument.

Option C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 12:04
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option c because reduction in % may be result of re categorization of passenger vehicle and not because of passenger vehicle efficiency.
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 12:18
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Answer is A as it is directly targeting the conclusion of the passage.
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 12:43
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A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged. Even if this is true, then the % decrease still holds.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet. Wrong. Effect of restriction cannot be evaluated.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels. Correct. This shows the shift in category of the same pollution level.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors. Irrelevant.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years. Wrong. While this does weaken, it is still not clear if the restrictions were not successful.


Ans C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 12:54
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Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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A) does not affect arguement in any way
B) alternate plan, but does not weaken
C)if true, this would weaken the argument. Since it is the alternate reason which could have atrributed to actually reduce the stats from 27 to 19%
D) not relevant as both situation could be counter balancing each other
E) This would strneegthen the last statement, that overall pollution increased. But does not affect the reasoning.

Answer is C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 12:58
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A. This does not directly address the issue at hand and in fact support the conclusion by the official
B This does not explain the referenced discrepancy at all hence incorrect
C If this is true it seriously weakens the reasoning behind the decline by showing an alternative explanation for the decline. Correct
D Traffic pattern changes do not necessarily explain the emission variances
E This does not undermine the main claim that vehicle improved standards have led to reduced emission
Ans C
Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 13:31
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Arguement core is since share of emissions percent attributed to passenger vehicles declined, hence stricter vehicle standards were effective in reducing pollution. But what if this decline is due to something else while pollution is still the same or more, that will weaken the statement above.

A) doesn't weaken as it says that the the total change was balanced, doesnt explain the above
B) since electric vehicles made a small share of the total, it doesnt help us in weakening
D) Yet again the both phenomenon balanced itself hence it doesnt weaken
E) Already stated in the last sentence of the arguement, doesnt add anything new

C) Here comes the real reason, the classification got changed, coz one category was removed from the passenger vehicles, leading to the fall in percent, but kept the pollution the same. Weakens the arguement that vehicle standards led to reduction in pollution.

Ans C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 13:40
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Official's reasoning: Stricter vehicle standards are effective in reducing air pollution

Basis: Share of emissions have declined from 27% to 19% over the last decade.

Fact: Satellite readings shows increase in air pollution.

(A), (B), (C), (D) - Irrelevant to the argument. Does not provide any information that could weaken official's argument.

(E) Cross-border haze events became more frequent, raising pollution in Velonia. This statement suggests that even though national emissions might have reduced, the rise in pollution could be due to cross border pollution. This directly weakens the official's reasoning, as he did not consider this factor while concluding low air pollution.

Hence (E) is the answer.
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 13:42
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Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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In the country of Velonia, environmental officials come up with a data on NATIONAL EMISSIONS to be discussed:

The OFFICIALS attributed that the SHARE OF NATIONAL EMISSIONS to passenger vehicles ( Pax Vehicles) has declined from 27% to 19% , that’s a 8 percentage points drop in the time span of 10 years.

The officials give credit to this drop to their STRINGENT vehicle standards have been effective in reducing overall air pollution. So, we can infer that there must have been a strict vehicle standards for all types of vehicles , and all that have contributed to reducing overall air pollutants.

The next line, mentions a shift from the earlier view - HOWEVER , satellite data paints a different picture for the same time frame. The amount of Total particulate pollution (TPP) has increased.

So, one side there is a figure citing reduction in national share of emissions by pax vehicles , and other side a completely gloomy picture of increased TPP.

We need to find a weakener among the options.

A) This is in complete contradiction to the stated facts. The option brings a terminology “new cars”, actually there is no distinction made between new and old cars. But, literally pax vehicles. Vehicles travelled a long distance, but the emission on per kilometre basis has reduced. Even though the percentage shows reduction, but the actual value remains unchanged. Meaning the strict rules have no effect to curb the pollution. Hence wrong.

B) If electric vehicles have been introduced , then this explains the reason for reduction of pollutants. Since, the occupy a smaller share. Their contribution towards emission reduction share is a matter of debate. Hence, nothing conclusive can be made. Wrong.

C) Five years ago, a major reclassification of vehicles happened, where several ride hailing fleets and small vans were changed from pax vehicle to light commercial vehicle. This reclassification resulted in vehicles being removed out of the pax vehicle category. Thus, their contribution to emission under pax vehicle category is not taken into account. Hence, pax vehicle showed a 8% point reduction. As the vehicles emission standards are not changed or addressed, they keep contributing to the overall pollution. THUS, increasing the TPP.

Hence, it’s not the strict vehicle regulations which has contributed to reducing emissions share of pax vehicles. A suitable weakening option.

D) This option debates on peak hour and non peak hour traffic. But, actually the number of vehicles plying the road and the emissions made still contribute to TPP and national emission share irrespective of the time they drive. Hence, wrong.

E) This explains a different possible reason why TPP had increased . But fails to explain the correlation between pax vehicle , national emission share and TPP. Hence, wrong.

Option C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 14:09
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Lets analyse, officials are basically saying :
1 ) evidence : the percentage of pollution coming from passenger cars went down ( from 27% to 19%)
2 ) conclusion : this proves our stricter rules for cars are working and are cleaning up the air

The report notes a big contradiction:
the officials says air is getting cleaner (due to car rules) and the satellite says the total pollution in country is actually getting worse.

how to weaken the officials claim : we need to show that officials evidence drop from 27% to 19% is misleading and doesnt prove that car rules are successful

lets check the options now:

option A : this is a strong weakener showing standards didnt reduce pollution, but C is better because it shows the reasoning itself is completely invalid due to an accounting trick

option B : this is a different cause for a potential reduction, it doesnt weaken the officials reasoning

option C : this shows officials key piece is just a change in paperwork, not a real environmental success from stricter standards. therefor officials reasoning is seriously weakened.

option D : this provides details on traffic patterns but doesnt clearly support or weaken the claim about overall vehicle emissions or standard effectiveness

option E : this explains why pollution increased, but it doesnt attack the officials claim that their car standards were effective

Therefor the correct answer is C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 14:44
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Option C

The claim is that decline in emissions is due to stricter standards for passenger vehicle.
But claim C clearly weakens the argument as ride hailing fleets and small vans which were reclassified as out of passenger vehicles and officials didn't take into account the emissions from these vehicles which makes claim misleading which undermines the conclusion.
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 15:08
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emission level has reduced.
reason is stricter vehicle standards reducing air pollution.
but at same time total pollution has increased.
B,D,E are not relevant at all. easy to eliminate.
A talking about kilometer travelling but thats not the issue. officials say the result came because of strict vehicle policy.
C talks about vehicles that have been moved from passenger vehicle category to others. so if thats the case then its not the strict regulation but change in vehicle identification led to reduction in emission while keeping overall pollution increased.
C is ans

Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 15:33
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Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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imo
Option C - Openly attacks the integrity of the data of the officials.
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 17:13
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Environmental Officials(EO) says:
National emission of PV decreases from 27->19% over last decade by having stricter vechile standard which responsible for lowering overall pollution(conclusion)
however
Satellite image say pollution has increased over the last decade.

This is a weakener we need to say stricter vechile was not responsible for lowering pollution
1)
challenges our conclusion that overall pollution by PV has not increased ,keep a
2) we do not know how big difference an EV makes and it doesn't related to stricter laws.out
3)reclassification couldn't contribute anything internal of over pollution. this shows that how data is being classified and not actual values i like this one
4)congestion and amount of wait has little to nothing to do with air pollution increase over large period
5) increase in pollution is due haze event being frequent than before this attacks the satellite conclusion, but we need to assume that emission by PV has decades. so don't like it i will go with C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 19:39
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Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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Premises:
Share of national emissions from passenger vehicles declined from 27% to 19% over the last decade

Satellite readings show Velonia's total particulate pollution has actually increased

Conclusion:
Stricter vehicle standards have been effective in reducing overall air pollution

The officials interpret a declining percentage share (27% to 19%) as evidence of reduced pollution from vehicle standards. However, a declining share doesn't necessarily mean absolute emissions from passenger vehicles actually decrease it could mean other emission sources grew faster, or the way emissions are categorized changed.


A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
This shows vehicle standards didn't reduce total passenger vehicle emissions, which weakens the effectiveness claim. However, it doesn't explain WHY the share declined from 27% to 19% if total emissions stayed the same.

B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
This supports rather than weakens the officials' claim about efforts to reduce vehicle emissions. The small share also makes this less impactful.

C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
This directly attacks the officials' evidence. The declining share is an reallocation of vehicles in one category to other, not an actual reduction in emissions. The same emissions are simply being counted under a different category, making the percentage drop meaningless as evidence of effectiveness.

D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
This describes traffic pattern changes but doesn't address whether the declining share represents real emission reductions or explain the gap in the officials' reasoning.

E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.
This could explain why total pollution increased in spite of domestic efforts, but it doesn't weaken the claim that vehicle standards reduced passenger vehicle emissions specifically.

Correct Answer C
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 19:53
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Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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Official's logic: Passengers' vehicle share of emissions fell, therefore vehicle standards reduced pollution.
Problem: A falling percentage doesn't mean falling pollution. Shares can fall even if nothing improves.

Option A: Says emissions stayed the same. Weakens a bit, but still compatible with standards, helping per car.
Option B: Irrelevant.
Option C: Perfectly weakens. It says pollution didn't fall; it just moved to another category, so stricter standards didn't cause the decline at all.
Option D: It's about the traffic pattern, nothing about emissions.
Option E: Explain higher pollution, but didn't challenge the vehicle-share claim directly.


Hence, OPTION C.
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 21:16
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The officials are celebrating a specific statistical trend: The "Share" of emissions from passenger vehicles dropped (27% \rightarrow 19%). They claim this proves their standards are working.

​And as per question we have to weaken officials reasoning, we need to show that the drop in numbers didn't happen because the cars got cleaner, but because of a Math Trick or a bad comparison.
​
IMO The correct answer is (C).

​Why (C) destroys the argument
​(C) Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
​The Logic:
Imagine you are trying to lose weight.
​Week 1: You weigh 200 lbs.
​Week 2: You weigh 180 lbs. You celebrate, "Wow, my diet is working!"

​The Reality (Option C): You didn't lose fat. You just chopped off your leg (or in this case, simply renamed 20 lbs of your body mass as "Not Body Mass").
​
In the context of the problem:
The officials are comparing "Passenger Vehicles" from 10 years ago (which included Ubers and delivery vans) to "Passenger Vehicles" today (which excludes them).
​
The "Passenger Vehicle" bar got smaller on the chart not because the cars stopped polluting, but because the government moved the numbers to a different spreadsheet column ("Light Commercial").
​
Since the prompt explicitly says this happened "without any change in their emission levels," the standards did nothing for these cars. The statistical drop is purely an administrative illusion.

​Why the others are incorrect
​
A. Per-kilometer emissions fell: This actually strengthens the idea that standards were effective. It says cars did get cleaner (per km), but population growth masked the total savings. The officials can still claim the standards worked (efficiency improved), even if volume grew.
​B. EV Incentives: This discusses how they tried to fix it (incentives), but doesn't explain the discrepancy in the data.
​D. Peak vs. Off-peak: This is just about when people drive. It doesn't explain the massive drop in the share of emissions.
​E. Cross-border haze: This attacks the Denominator (Total Pollution).
​The Logic: If Total Pollution (Denominator) goes up due to haze, the Vehicle Share (Numerator / Denominator) will mathematically drop.
​Why C is better: While E is a valid weakener (the drop is due to math, not policy), C is a fatal flaw. Option C proves the officials are using a corrupted definition of their own metric. Comparing "All Cars" to "Some Cars" is a fundamental logic error, whereas Option E just suggests the trend is misinterpreted.

Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 21:30
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Premise: Natural vehicle emissions declined from 27% to 19% over the last decade. But total particulate pollution has increased
Conclusion: Stricter vehicle standards have been effective in reducing overall air pollution
Logical gap: The percentage share of vehicle emissions have decreased. This does not mean that vehicle emission has indeed decreased. It might also be the case that the overall emissions has significantly increased and hence the share of vehicle emissions in the whole of polution has decreased

Evaluating answer choices

A) This weakens the reasoning of official. Since total emissions are unchanged, the contribution of vehicle emissions have also not changed. This in fact goes against the conclusion that stricter vehicle standards have reduced air pollution. Also this does not explain why total particulate pollution has increased in the mean time
B) Since the electrical vehicles make up only a small proportion, we cannot conclude that the shift to electrical vehicles have reduced pollution significantly. Also this does not explain overall increase in pollution
C) This change in classification does not concern the emission levels
D) This statement says that the vehicles are just displaced now leading to no reduction to emissions.
E) This gives a bigger reason for higher particulate pollution in the recent years. The frequent cross-border events has increased the overall pollution. So the share of vehicle emissions to overall pollutions has decreased without actually reducing the vehicle emissions. This explains the contradictory observation in the argument and also breaks the reasoning of official that the vehicle emissions have indeed reduced due to stricter vehicle standards
Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged.
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors.
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years.

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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 21:47
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I chose C.


See reasoning below:

Bunuel
Environmental officials in Velonia note that the share of national emissions attributed to passenger vehicles has declined from 27 percent to 19 percent over the last decade. They cite this trend as evidence that stricter vehicle standards have been effective in reducing overall air pollution. However, satellite readings over the same period show that Velonia’s total particulate pollution has actually increased.

Which of the following, if true, most seriously weakens the officials’ reasoning?

A. Vehicle kilometers traveled rose sharply as Velonia’s population grew, while per-kilometer emissions from new cars fell, leaving total passenger-vehicle emissions roughly unchanged. We are told the % of emission for passenger vehicles declined in relation to total emissions. If this were the case 27% would still be 27%
B. During the same decade, Velonia implemented incentives for electric vehicle adoption, though these vehicles still make up a small share of the national fleet. Neat fact, but if they only make up a small share of the national fleet, it wouldn't make a meaningful impact.
C. Five years ago, the national inventory reclassified emissions from ride-hailing fleets and small delivery vans from “passenger vehicles” to “light commercial transport,” without any change in their emission levels. Reducing the number of vehicles that are considered passenger vehicles will regardless of new emission policy.
D. Peak-hour traffic fell in several city centers after congestion fees were introduced, though off-peak traffic increased in suburban corridors. Traffic moved from one area to another. | out-of scope
E. Regional cross-border haze events became more frequent, raising measured ambient pollution in Velonia during several recent years. Irrelevant
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Reducing the contributors to an overall number will meaningfully impact that number.
Option C would be akin to saying.

Tom took the GMAT and scored Q60 V90 and DI66. Tom studied for 10 months and retook the test. Tom scored an 805.

Hidden behind the 805 is option C, where Tom is allowed to drop 2 sections of his score. Tom drops Quant and DI, and is left with V90, while claiming and 805...
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12 Days of Christmas GMAT Competition 2025 - Day 2: Environmental 16 Dec 2025, 23:03
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IMO answer is C.

A. Irrelevant as it shows that the overall pollution remains unchanged while satellite shows increase.
B. Adoption of electric car is good to show the decline but makes up for a small share of total population which doesn't properly justify the decline.
C. Bingo! They reclassified certain vehicles from passenger vehicle category to something else. So a chunk of population was removed from the data which shows the decline but still has the same emission.
D. Irrelevant
E. Introduces another factor of causal but does not affect the conclusion that stricter standards were effective in reducing the emission
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