CR question from GMAT prep

[sudaif]

Nitrogen dioxide is a pollutant emitted by automobiles. Catalytic converters, devices designed to reduce nitrogen dioxide emissions, have been required in all new cars in Donia since 1993 and as a result, nitrogen dioxide emissions have been significantly reduced throughout most of the country. Yet although the proportion of new cars in Donia's capital city has always been comparatively high, nitrogen dioxide emissions there have showed only an insignificant decline since 1993.

Which of the following, if true, most helps to explain the insignificant decline in nitrogen dioxide emissions in Donia's capital city?

A. More of the cars in Donia's capital city were made before 1993 than after 1993
B. The number of new cars sold per year in Donia has declined slightly since 1993.
C. Pollutants other than nitrogen dioxide that are emitted by automobiles have also been significantly reduced in Donia since 1993.
D. Many Donians who own cars made before 1993 have had catalytic converters installed in their cars
E. Most car trips in Donia's capital city are too short for the catalytic converter to reach its effective working temperature.

I get E is probably the best choice but unsure about A and B.
Specifically:
A) --- if there are less new cars relative to old cars in the capital, then wouldn't that help explain why reduction of NO2 has been insignificant? The only mitigant that I could think of to that was -- they are talking about all cars "sold" and not "made" after 1993. It is possible that the car was made before 1933 but when it was sold after 1933, it was required to have the Catalytic converter.
B) --- if the number of new cars have declined -- doesn't that help explain why NO2 reduction has been insignificant? That is, there are more old cars on the road and they don't have Catalytic converters.
help!

[tim]

A presents irrelevant information; we are told that the capital city's proportion of new cars has always been high, so the status of the other cars doesn't really matter. B has exactly the same problem..

[krishna260810]

What is the OA ?
I think its shall be D . Pls confirm.

Regards
K

[RonPurewal]

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gmatprep-cr-question-t9180.html