A law passed five years ago requires all new cars sold in

Question

A law passed five years ago requires all new cars sold in Mauritania to be equipped with catalytic converters which decrease vehicular emissions of nitrogen dioxide. Emissions of nitrogen dioxide have significantly decreased throughout Mauritania, except in one particular city. Over the past 5 years, this particular city has had the highest rate of new car sales of any city in Mauritania, yet its nitrogen dioxide emissions remain unchanged from those prior to the passage of the above referenced law. 

Which of the following best explains the discrepancy?

A. A higher percentage of cars made prior to the enactment of the law operate in the above city
B. The rate of new car sales has dropped moderately since the passage of the law
C. Nitrogen dioxide is not the only pollutant whose emissions have decreased since the passage of the law
D. The referenced law did not require owners of cars made before its passage to retrofit their cars with catalytic converters
E. The average drive time of the average car trip in this particular city does not allow sufficient drive time for the catalytic converters to reach optimal efficiency

johnycute · Answer

Clearly its E.

If catalytic converters can not reach to their efficiancy there is no use of catalytic converter and the pollution will remain same.

buckkitty · Answer

Between A and D, I pick A.
the only way to explain the unchange level of ND emissions is to find some other factor that would increase ND even though the new law decreases ND. >>higher number of older cars in this cit. So even though new cars emit less ND, more older cars will make up the difference.

B-not concerned about total new car sales, only with sales in the one city
C-other pollutants -out of scope
D-very close. But we cannot say that this has a direct effect on this city. What if they do not have any cars older than the new law?
E-optimal efficiency? to vague to explain discrepency

jamesrwright3 · Answer

I got this question from another board and I said A as well
Many other people thought E
Actually I was the only one that thought A worked and E didn't 

Here is the reason E doesn't work for me..

Say the average drive time in the city with the highest pollution is 15 minutes compared to a 30 minutes in the other cities. Say for example the optimum time to hit catalytic converter efficiency is 15 minutes. So, for the first 15 minutes in ANY city you are going to get the SAME AMOUNT of nitrogen output. Hence, the cities with the longer drive time would actually have MORE pollution since they would be putting out the same amount as the city with the highest pollution for the first 15 minutes at least and then still putting more out (but at a lesser rate) for the next 15 minutes.

ncp · Answer

I will also go with A. 

E simply says that the efficiency is not optimal. It does not mean that the converters do not work. Which indicates that there is another reason,unrelated to the sale/operation new cars, for the discrepancy.

A supplies this reason.

mm007 · Answer

A for the same reason, also by POE.. 

E is talking about efficiency, which does not help.. as an analogy so what if the bulb is dimly lit, it is still lighting the place.

jamesrwright3 · Answer

I am glad you guys agree with me
I was beginning to feel dumb!

Sumithra · Answer

I vote for A.

So, you don't have OA?

jainan24 · Answer

I had chosen A too

jamesrwright3 · Answer

Well there was no OE on the board where I got it from
I had seen this question somewhere before though-not sure where
Maybe the RC 1000 set? or on another boards "Super Good" gmat examples...I won't name the board but it helps you get a top score (reverse the words)
Everyone on there thought it was E. I was one of two who thought it was A

Andr359 · Answer

By POE and comparing/contrasting answer choices: B is not so relevant. C is rather irrelevant. D is not so relevant either. Remember that the best answer is the most direct path between the question and the stem. E could explain the discrepancy. A as well.

A law passed five years ago requires all new cars sold in

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