In 1986, the city of Los Diablos had 20 days on which air pollution re

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

its B.

its not D because D says

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.

Now how does one know that the pollution was because of industries and not because of say a large amount of cars on the road.

1) Picture what's going on in this question through visualization in your head.

The # of days for "unhealthy" pollution levels rose from 20 days, to 31, 39, then dropped to 16 in the last year.

2) Something must explain why the numbers rose then fell. We know there was some control measures enacted in 1987 (the second year). But we then see an increase then a decrease 2 years later. Why?

(A) Helps explain - if they were not put into effect until end of 1988, we wouldn't see results until 1989 (the last year)

(B) Does not explain - the idea of a new gas spectrometer being invented is not linked to the counting of unhealthy days NOR is it linked to any increase then decrease in # of unhealthy days. Inventing an instrument has no effect on data - unless there's a specific link - the closest possible link is that all the data was bogus before and only the last year was accurate because a more accurate instrument was used and captured a far lower figure. But since the drop is so big, this possibility is extremely unlikely.

(C) Helps Explain - By revising the scale, what is considered harmful enough to count as an "unhealthy" day will drastically affect the numbers. What may have been 30 days under the old scale, could suddenly drop down to 16. So this could help explain (if implemented in the last year) why that last year figure is so low

(D) Helps Explain - 1988 levels were really high - might have been because the mayor accepted donations and he let industries pollute more that year

(E) Helps Explain - well if it takes 2 years in atmosphere to see the results, that's prob why we still had 2 bad years (tho mb doesn't explain the increase). Then in the last year it drops.

Hope that helps!

Hi TheNona,

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.

The question asks us to find an answer choice that is LEAST helpful in explaining the pollution levels between 1986 and 1989. (B) may explain why the smog alerts decreased in 1989, but it will not explain the rise in pollution level in 1987 or 1988.

(D) on the other hand helps to explain the levels, because the Mayor "was found" to have accepted donations and exempted industries from pollution control measures. In 1988 it was found, so it is possible that he could have been taking donations in the past also; it could explain the pollution levels in 1987 and 1988. Thus, (D) explains.

Hope this helps,

Vercules

In 1986 20 days .
In early 1987, new air pollution control measures were enacted, 31 days
In 1988 39 days.
In 1989 16 days.

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.
Put into effect at the end of 1988, so the result will be seen in 1989. That's what happens (only 16 in 89), so it's a good explanation
(B) In December of 1988, a new and far more accurate gas spectrometer was invented.
CORRECT
(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.
Review of the scale , raising or lowering the levels (we do not know). Take the case of higher levels => less days of high pollution. It could explain the drop in 89.
(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
So in the years prior to 88 the high levels were caused by those industries. In 89 those industries will not cause high pollution=> drop in 89. Good explanation
(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area.
So the pollution will remain in the air for 2 years minimum. We'll se the result of the 87's mesures in 89(2 years later). That's what happens, so is a good explanation

Argument:
In los Diablos smog alerts happens when air pollution reached unhealthful amounts.
Fact1: 1986- smog alerts on 20 days
Fact2: early 1987- new air pollution control measures were enacted.
Fact3: 1987-smog alerts on 31 days
Fact4: 1988- smog alerts on 39 days
Fact5: 1989- smog alerts on 16 days
Fact6: 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.

Pre thinking
According to fact the main air pollutants are ozone and carbon monoxide and both are monitored using gas spectrography since 1986 so measuring technique can’t be cause of pollution change unless some changes happens in gas spectrography.
Pollution controls were enacted in early 1987 and pollution actually rose after that till 1988 and then came down in 1989.Looks like it took some time for the effects of measures taken in 1987 to start controlling pollution.

Analysis of answer choices:
(A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988.
INCORRECT: This helps in understanding why it took time for pollution to go down by 1989.

(B) In December of 1988, a new and far more accurate gas spectrometer was invented.
INCORRECT: This can help in understanding the reading difference in 1989 if we assume that the gas spectrometers earlier were giving higher readings than the real readings. Also we have to assume that control measures were not having much effect and thus pollution increased from 1986 to 1988.
(C) In February of 1989, the Pollution Control Board of Los Diablos revised the scale used to determine the amount of air pollution considered un healthful.
INCORRECT: This can helps us in understanding why pollution alerts went down in 1989 if we assume that the level for un healthful was raised. Also we have to assume that control measures were not having much effect and thus pollution increased from 1986 to 1988.

(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.
CORRECT: this means that lesser industries are using air pollution control measures and hence air pollution should go up. However its went down in 1989 and it can’t be explained from this answer choice.

(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area.
INCORRECT: This helps in understanding why it took time for pollution to go down by 1989.

So D in my opinion as well . I believe official answer is incorrect.

My initial pick was D too. But I guess after reading it the second time , I see why B makes sense.


As other people have pointed out , it only says spectrometer was invented . No mention of it being used to monitor the levels.


No doubt , the pollution increases , if mayor exempts those industries from air pollution measures. So accepting donations to exempt those industries , meant increase in air pollution. If we focus on the bold part above in D , it says in 1988 , the mayor was found to have accepted. It doesn't say that mayor ACCEPTED in 1988 and EXEMPTED the industries IN 1988. He was FOUND to have accepted in 1988. He might have accepted the donations before 1988 or in the middle of 1998 or end of 1988.They just found that thing in 1988. The exemption might have happened in 1987. Or if they found out by the end of 1988 , then exemption might have happened till they found out , in 1988. This kinda explains why the pollution increased till 1988. And mebbe once they found out in 1988 , what mayor had done , they might have reverted the exemptions , which is why in 1989 pollution went down . I know it is bit of a stretch to make these assumptions , but when we are to choose between B and D (In B - where you make an assumption that invented meant used + cant justify yet as to why did new and accurate instruments show lower pollution levels) , the assumptions what we made in D seems safer.

HTH
Jyothi

For me, B is correct. My analysis is below...

Structure
Contrasting Fact 1:
In 1986, City LD had 20 days on which air pollution reached unhealthful amounts --> Smog alert into effect.
In early 1987, new air pollution control measures were enacted, but[/highlig[highlight]ht] LD had smog alerts on 31 days that year and on 39 days in 1988.

Contrasting Fact 2:
In 1989, however, the number of smog alerts in LD dropped to sixteen.

LD's main air pollutants: O3 & CO,
Since 1986 the levels of both have been monitored by gas spectrography.

Pre-thinking
We have to find the option that explains the least the contrasting facts. So we can star by pre-thinking some explanations of both contrasting facts:
What if levels of both pollutants remain in the environment for at least two years?
What if pollutants' limit levels were drop significantly in 1987 when the new control measures were enacted?
What if gas spectrography device was not correctly caliber?

Answer choice analysis
(A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988. Correct
Help to explain Both contrasting points. this option would justify the rise in the number of alerts in the city for both 1987 and 1987; and the drop of alerts in 1989.

(B) In December of 1988, a new and far more accurate gas spectrometer was invented. Incorrect, so correct choice!
This option is OFS. The invention of a more accurate gas spectrometer doesn't mean that LD city used them to measure pollution.

(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. Correct!
Aligned with pre-thinking.. in the revision they probably increase the pollution limit, so this fact explains a drop in the number of alerts.

(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. Correct
If he accepted money in exchange for an exemption of the execution of measures, those local industries, knowing that were not going to be punished, were deliberatly contaminating the environment, explaining the high number of alerts during 1987 and 1988. Then, a drop on alters in 1989 happened after the mayor was found to receive bribes.

(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area. Correct
Aligned with pre-thinking.

Hope the analysis helps!

Hi jedit ,

B is the correct answer and has been very well explained above.

Let me know your specific doubts so that I can help get those resolved.

Just remember one thing:

The question is about LEAST explain.

B is saying they got more accurate. If they got more accurate, they should have increased the number of days rather than decreasing the count.

D is correct. It doesnt explain anything. Readings are taken at neutral sites, so won't be impacted by clandestine deals.

B does explain. All readings prior to 89 had large margin of error so were probably false.

That's the best possible solution.

Posted from my mobile device

Well could I argue that a more accurate gas spectrometer will more accurately identify ozone and carbon monoxide, and hence giving less false alarm. In this case B, would be helpful.

As much as I want to agree with you, but unfortunately, an incident of a false alarm is out of scope of the question stem. One can only answer CR questions if and only if the reasoning is clearly inferred from the information provided.

Cheers!

This was interesting:

I leaned towards E because of:

(A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988.

If A is true, then E is not helpful in anyway. But I guess I should not have taken A to be true as the options may or may not contradict each other and are not parts of the prompt.

I believe the question stem is purposely trying to “hide the ball” and making it hard for us to figure out what exactly it is we are supposed to explain. In doing so, depending on how you word what it is we are trying to explain, you could interpret the answers a few ways.

My interpretation of what we are being asked to explain is the following:

We have this weird anomaly.

In 1986, there is 20 days of bad pollution measured.

Then, in early 1987, pollution control measures are put in place. However, the pollution INCREASES in 1987 and 1988 despite these new measures.

Then, in 1989, the pollution finally dropped to an amount below 1986’s level - an effect one would expect to occur after new pollution measures were put in place (just not 2 years after the fact).

So why did pollution go UP in 1987 and 1988 after the pollution control measures were put in place in early 1987? Why did it take 2 years for these measures to finally make a difference in the pollution levels?

-A- Tells us that these pollution measures, although passed, weren’t enacted until the end of 1988. This means that they wouldn’t have had an effect on 1987’s and 1988’s pollution levels

We still don’t have an explanation as to why the pollution increased from 1986 through 1988. However, we do have an explanation as to why it took so long to see any pollution reduction after the measures were passed in early 1987.

I believe A would be useful in answering why the pollution levels between 1986 and 1989 were they way they were (though not perfect). You can eliminate A.

-C- If, in February 1989, the scale used to measure the pollution was adjusted, then this fact might explain why the pollution levels didn’t reduce until 2 years after the measures were passed. This fact could indicate that the measures didn’t have any effect on the reductions in 1989: the true cause was this new scale put in place that made the 1989 levels appear lower than they actually are (though this thought process also comes with assumptions).

We still do not really have an answer to the following question: why did the pollution levels first go up after the measures were put in place in early 1987?

I would keep this one for now.

-D- If, in 1988, the mayor was found to have looked the other way regarding certain industries and their pollution practices, then this could possibly explain why the measures didn’t work right away in 1987 and 1988.

But was he also the mayor in 1989? Or Did a new mayor come in? Did this new mayor finally follow these passed pollution control measures passed in early 1987, such that pollution levels finally went down in 1989?

I eliminated D, but I can see everyone’s argument and point of view.

I do believe though that if we use the “common sense connections” analysis the GMAT so highly advocates, then we can put together the following:

If the mayor were being bribed to look the other way, then this would explain why the pollution measures didn’t work right away in the beginning.

Also, if we know now about this bribery (so presumably the public would know also), it would make sense that either this mayor or a new one would not be able to get away with looking the other way again in 1989. He or she would have to finally start adhering to the pollution control measures.

This could possibly explain why the pollution control measures finally started to work in 1989.

I would eliminate D for that reason.

-E- we are told that it take the pollutants causing the issues 2 years to break down. Thus, if the pollution control measures were put in place in early 1987, then it would make sense that we wouldn’t see an effect until 1989 (however, we still don’t really have a clear explanation as to why an increase in pollution occurred in 1987 and 1988 after the measures were passed).

I still believe E gives us an idea about some of the reasons why the pollution levels behaved the way they did. I would eliminate E.

-B- in late 1988, a far more accurate device that is used to measure the pollution was invented.

The problem with B is that there are just too many questions left open, even more questions then the other answer choices leave us asking.

Was this new device used to measure the readings actually used in 1989? Knowing that it was invented and it is “more accurate” isn’t a helpful fact if it was never used in the first place.

Even through we have a new device that is “more accurate,” this doesn’t mean the old device was necessarily bad. And even if the old device was bad, why is it that the pollution levels were at 20, then after pollution control measures were enacted, the levels shot up for 2 years?

Even with a bad device, the pollution levels being measured are relative. We don’t have any explanation about why the levels went up for 2 years AFTER pollution measures were adopted.

For this reason, I believe B does the least to explain the pattern of pollution.


I also think this is the underlying issue that the question is trying to get at. Just because the reader used us more accurate later on, it doesn’t explain why there was this relative increase in 1987 and 1988 compared with 1986 when there should have been a relative reduction after the pollution control measures were passed.

Is there any word on if this question is official?





Posted from my mobile device

Invented but not implemented. So D is not the answer.

The reason B sounds a little absurd that it can help either increase or decrease both , so it seems to be helpful




Posted from my mobile device

Argument
New control measures were enacted. But for first two years situation worsened and then it reversed directions dramatically

Question Type
Describe the discrepancy + LEAST -> 4 will support the theory, one won't

(A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988. --> if control measures were put into effect in November 1988, that means the quality will be effected positively from then onwards. So it explains why situation improved --> Explains the discrepancy --> Wrong

(B) In December of 1988 a new and far more accurate gas spectrometer was invented. --> Good to know that. But accuracy won't change bad outcomes --> Doesn't do anything to explain the discrepancy --> CORRECT Answer

(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. --> Ok.. So now even unhealthy air is considered healthy --> so some days when it is less unhealthy, those days will be considered healthy --> This will decrease number of days of unhealthy air --> Explains the discrepancy --> Wrong


(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. --> Oh so mayor had taken some money before 1988, and after this discovery may be these industries were regulated as per standard leading to decrease in pollution and hence lower pollution --> Explains the discrepancy --> Wrong

(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area. --> So measures took two years to become effective. So things went back to normal after two years. This explains ti --> --> Explains the discrepancy --> Wrong