At first glance A is attractive, however this is answer is wrong for a similar reason that percent-style answers are often wrong. Take the following scenario with regard to A): the country folk reduce their pre-1993 car population from 100% to 70%, which creates a significant reduction in nitrogen pollution.

So far so good, this scenario doesn't deviate from the conditions in the argument.

Then say the city slickers do the same, but even more so, from 100% to 51%.

Again this is fine, the argument says that the city slickers are more likely to buy new cars.

So in the above scenario, we satisfy all the condition of the argument. We have also satisfied A) because there are 51% 'old cars' in the city, which means there are more old cars than new. However, given that we see a significant drop in pollution nationally with a 0% to 30% increase in new cars, shouldn't we expect to see a much greater improvement in the city if we have 0% to 49% uptake of new cars? This argument actually takes us the other way! A) cannot be correct because it brings us no closer to bridging the discrepancy.

For those that are interested, E) is correct because it bridges the gap between the 'expected' and the actual. It does so by accounting for the increase in new cars in the city, while offering a reason why this hasn't had an effect. The reason being that new cars require a minimum distance to be eco-friendly and this distance is rarely reached. In other words, the solution is ineffectual.

Hope that helps!
B.

C is out as we are bothered about other pollutants.
D, if true, would weaken the claim

Out of A, B & E, I can eliminate B as the no. of cars sold has declined only "slightly", so it doesn't support the insignificant decline in the emissions.

Out of A & E, E helps to explain the situation better as even though more cars are made before 1993 than after, still some cars are made which should have reduced the emissions.

My choice - E.

Is it E ?

agree with the above explanation. Is the answer E ?

Between A and E,

E) is better since if converter does not work the levels wont decrease

A. More of the cars in Donia’s capital city were made before 1993 than after 1993---Good incorrect choice. But we are still told that there are comparatively high no. of new cars, therefore a significant drop should have been there
B. The number of new cars sold per year in Donia has declined slightly since 1993-----weakens. If it has declined only slightly then a significant decline in emissions should have been seen.
C. Pollutants other than nitrogen dioxide that are emitted by automobiles have also been significantly reduced in Donia since 1993.---------out of scope
D. Many Donians who own cars made before 1993 have had catalytic converters installed in their cars. Does not explain the contrast
E. Most car trips in Donia’s capital city are too short for the catalytic converter to reach its effective working temperature------CORRECT

Nitrogen dioxide emissions have been significantly reduced throughout most of the country as given in the argument
that means catalytic converter was actually performing its function; If it didn't than Nitrogen dioxide wouldn't have reduced at the first place.


If my understanding is incorrect please explain what role this statement plays :-
"nitrogen dioxide emissions have been significantly reduced throughout most of the country".

You are right. The answer for this question is (E).
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Hi,

Most car trips in Donia’s capital city are too short for the catalytic converter to reach its effective working temperature

Dont you think the information marked above in red is out of bounds of the stimulus. If so how can option E be correct?

Look, there are two different things. One is '[highlight]new information[/highlight]'. Your options playing the role of premises provide new information to strengthen the conclusion/weaken the conclusion/explain the paradox.
The other thing is '[highlight]out of scope[/highlight]' i.e. when the option discusses something irrelevant to the argument. e.g. if I say "The country Monia's capital has witnesses a massive decline in nitrogen dioxide emissions since they introduced catalytic converters." This is out of scope because what happens in country Monia has nothing to do with what happens in country Donia.

The information in red is new information which explains the paradox that though in Donia nitrogen dioxide emissions have reduced significantly, they haven't reduced in Donia's capital. In Donia's capital, people don't travel long distances and hence the catalytic converters doesn't reach their effective working temperature.
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I totally agree with Karishma. In fact, most of the times, we can answer strengthen/weaken/paradox questions by bringing " relevant additional info". Only for assumption questions, we have to confine to the argument.

it is very well mentioned that "..............Yet although the proportion of new cars in Donia's capital city has always been comparatively high"
so, (A) can not be considered correct.

(E) wins because the catalytic converter installed in the new cars are not effective , so the purpose of emission reduction failed.

Aah!! the famous trap of differing groups.
while the opening sentences talk about Donia as a country, the argument quickly shifts to the capital city.
the statement -


moves the focus from the nation to its capital.
also, the question asks us about the capital city.

so, knowing that proportion of new cars in Donia's capital city is more than old cars, how can we not rule out option A which mentions just the opposite.


look out for option choices involving only Donia's capital city and apply POE to them.

Lets plug in numbers so that A is ruled out , lets say we have 1000 cars in capital , 510 , 490 would be the respective numbers of cars produced before and after 1993. 490 could represent lets say a very high proportion of new cars in Donia ie 50% , the argument says that the corresponding decrease that should have been attributed to these 490*50/100 cars has not been seen. Hope it makes sense now. Option A only plays with numbers without actually justifying the argument gap

Strategy for resolve the paradox question, Before attacking the choices keep the following rule in mind:
1. An answer choice would be wrong if it negates any FACT given in argument.
2. An answer choice would be wrong if it supports or weaken the Conclusion.
3. An answer choice would be wrong if it talks about Y when we are concerned about X.

A. More of the cars in Donia's capital city were made before 1993 than after 1993.
More of the cars - this is not strong reason.

B. The number of new cars sold per year in Donia has declined slightly since 1993.
negates the info given in argument : the proportion of new cars in Donia's capital city has always been comparatively high

C. Pollutants other than nitrogen dioxide that are emitted by automobiles have also been significantly reduced in Donia since 1993.
Only "nitrogen dioxide emissions" are relevant.

D. Many Donians who own cars made before 1993 have had catalytic converters installed in their cars.
this one is a Weakener not resolving the issue.

E. Most car trips in Donia's capital city are too short for the catalytic converter to reach its effective working temperature.
So what we think should reduce the emission is not even used because of this reason mentioned in E. Resolves the WHY.
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E is correct.

I had it down to A and E - A is incorrect because it is said in the main stem that the capital has a higher proportion of new cars which makes this statement contradictory to the assumption made in the stem.

in gmat, an explanation question does not need to have the scope that fits the argument. E may seem to be a weird answer, but E is the correct one.

Argument - Catalytic converters (CC) --> reduce nitrogen dioxide (NO2) emissions.
- It is mandatory to fit CC in all new cars since 1993.
- Nationwide effect = NO2 emissions have decreased.
- Paradox = Nationwide there is a decrease, however, in capital city which has highest proportions of new cars has experienced a insignificant decline.

(A) More of the cars in Donia's capital city were made before 1993 than after 1993.
- The choice goes against the evidence given in the passage. The passage clearly states that proportion of new cars is higher than it is in entire nation.
- Wrong

(B) The number of new cars sold per year in Donia has declined slightly since 1993.
- These sales figures are immaterial. As long as the evidence of higher proportion of new cars is not refuted. The sales figures do not impact the argument
- Wrong

(C) Pollutants other than nitrogen dioxide that are emitted by automobiles have also been significantly reduced in Donia since 1993.
- This option could have been a contender had the passage spoken about the percentage of nitrogen emission of the total emissions.
- However, the argument clearly mentions the absolute number.
- Wrong

(D) Many Donians who own cars made before 1993 have had catalytic converters installed in their cars.
- The proportion of the owners with cars made before 1993 is less in the capital city. Hence, compared to the nation a fewer number of individuals with cars made before 1993 must have installed the CC.
- Thus we can say that the impact of decrease in NO2 emissions because of installing of CC in cars made before 1993 is higher in the entire nation compared to the impact in capital city.
- However we are not sure about the percentage of population owning cars made before 1993 that installed the CC.
- May be no one installed the CC, may be everyone installed the CC
- Wrong

(E) Most car trips in Donia's capital city are too short for the catalytic converter to reach its effective working temperature.
- If CC cannot reach its effective temperature --> it is not able to filter NO2 emissions - Explains the paradox
- Correct

Can someone please explain me to get the crux of this argument. I also wanted to know how other options are eliminated and how the correct answer is correct.