In 1986, the city of Los Diablos had 20 days on which air pollution reached unhealthful amounts and a smog alert was put into effect. In early 1987, new air pollution control measures were enacted, but the city had smog alerts on 31 days that year and on 39 days the following year. In 1989, however, the number of smog alerts in Los Diablos dropped to sixteen. The main air pollutants in Los Diablos are ozone and carbon monoxide, and since 1986 the levels of both have been monitored by gas spectrography.
Which of the following statements, assuming that each is true, would be LEAST helpful in explaining the air pollution levels in Los Diablos between 1986 and 1989?

(A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988.
(B) In December of 1988 a new and far more accurate gas spectrometer was invented.
(C) In February of 1989, the Pollution Control Board of Los Diablos revised the scale used to determine the amount of air pollution considered unhealthful.
(D) In 1988 the mayor of Los Diablos was found to have accepted large campaign donations from local industries and to have exempted those same industries from air pollution control measures.
(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area.
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D

I actually thought that E, if true, would be one of the most eloquent explanations, so I wouldn't have considered E at all.

The answer is B. The reason it is the answer is because it says the new system was more accurate. Being more accurate doesn't mean that the old results are not true, it only means that they are now more certain about the levels. It does the least to tells us that that what is in the passage is true, because with B we're not certain whether the new gas spectrometer helped or made worse the evidence in the passage.

E helps because it tells us why in 1989 we started to see such a drastic drop.

D helps because it would give a good reason why the drop in incidences began.

I hope this helps.

Jared

B states; In December of 1988 a new and far more accurate gas spectrometer was invented. The question stem says that we must assume this is true. I'm using certainty and accuracy as synonyms. The more accurate the results are the more certain you can be of those results. How could something be more accurate and not more certain. Regardless, the point is that in this particular question we are looking for the answer that is least helpful in explaining the air pollution levels. In order for B to be helpful there would have to be other information involved; for example;

1. They could actually use this gas spectrometer.
2. More accurate results would lead cause the number of smog alerts to increase and not decrease.
3. It wouldn't take a ridiculous amount of time to determine the results of the info gather by the new technology.

I could come up with more examples, but you get the picture. In order for B to be helpful we would need additional information, which is not provided in the passage.

Again I'll go through why the other choices are helpful.

A. They didn't put the laws into affect until the end of 1988, which would be a good reason why the level did not drop until 1989.
C. In 1989 they came up with a new scale which could be a good reason why the number started dropping so drastically. The new scale was less sensitive to smog levels.
D. Would be a good reason why the number of days dropped because it shows the drop is not do to decreased smog level but instead is due to the inspectors taking less readings.
E. This would be a good reason because it would mean that measures enacted in 1987 did not have an impact until 1989.

Hope this helps.

What is the OA?

Thanks,

Jared

Regarding D,

Doesn't it go against the given information? In '89, the smog # went down. However, if the mayor exempted companies from pollution control, there would be MORE pollution, and hence MORE smog #.

Therefore, it doesn't help in explaining why the number went down.

Why is this thinking wrong?

hmm....

I narrowed down between A and B but was not sure how to interpret, "more accurate gas spectrometer".

Hi guys,

Thanks for the explanation above.

But just to add, I feel B states that new instrument was INVENTED, as per the question we must believe it was invented but we can not assume that the same instrument was installed or used.

Hope my reasoning is right.

Thanks,

i will go with option 'b' ,inventing an equipment does not mean helpful in explaining pollution levels.
coming to 'd'-if industries are exempted from pollution laws,it will effect the pollution levels.
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in-1986-the-city-of-los-diablos-had-20-days-on-which-air-32988.html?fl=similar

OA in the above post its B