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标题: [求助]gwd11-20 [打印本页]

作者: ilovecushi 时间: 2007-11-6 15:50
标题: [求助]gwd11-20

Q20:

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?

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

no one has discuss this question before..

is it too easy?

the answer is E. but why A is wrong?

A did tell a reason that the nitrogen dioxide emission is insignificant, didn't it?

作者: simonshen 时间: 2007-11-6 22:36

E肯定对是无须质疑的,因为在首都往往路程太短,催化转换器没法达到最佳工作温度,所以装了也是白装,所以自从93年要求强制安装以来也只有微小改善.

A说在首都,93年前造的车比93年后造的车多,但这不说明什么问题.93年后造的车都是装了converter的,如果converter有效,那还是会较大程度上减排废气的.所以这个A不怎么说明问题,相比较E明确得多.

作者: ilovecushi 时间: 2007-11-7 06:07

i got it. thank u for ur kindly explanation!

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