In 2009, the city of Los Bernardinos ranked worst nationwide wit

In 2009, the city of Los Bernardinos ranked worst nationwide with 148 days of unhealthy air after a report was published by the Environmental Protection Agency. In early 2010, a series of pollution control measures were enacted by local government. Still, that year the city recorded smog alerts on 153 days and 160 days the following year. In 2012, however, the number of smog alerts in Los Bernardinos dropped to 118. Air pollutants from cars, buses and trucks, particularly ground-level ozone and particulate matter, can worsen respiratory diseases and trigger asthma attacks. These pollutants have been measured by gas spectrography from 2009-2012.

Which of the following statements, assuming that each is true, would be LEAST helpful in explaining the air pollution levels in Los Bernardinos between 2009 and 2012?

A. The 2010 air pollution control measures enacted in Los Bernardinos were put into effect in 2012..........explains the paradox

B. In early 2012, the Pollution Control Board of Los Bernardinos revised the scale used to determine the amount of air pollution considered unhealthful.........................explains the paradox

C. In early 2012, a new and far more accurate gas spectrometer was invented...........explains the paradox

D. In 2011, the mayor of Los Bernardinos was found to have accepted large campaign donations from local industries and to have exempted those same industries from air pollution control measures.............does not explain why the smog alerts dropped if the pollution increased

E. Excess ozone and carbon monoxide (some of the air pollution particulates measured) require a minimum of two years to break down naturally in the atmosphere above a given area...........explains the paradox

Here is my analysis. Please explain why C is right and D is wrong.

tough one, was struck between C and E.


Which of the following statements, assuming that each is true, would be LEAST helpful in explaining the air pollution levels in Los Bernardinos between 2009 and 2012?

A. The 2010 air pollution control measures enacted in Los Bernardinos were put into effect in 2012.
now this explains why in 2010 and 2011 the # of days did not drop.

B. In early 2012, the Pollution Control Board of Los Bernardinos revised the scale used to determine the amount of air pollution considered unhealthful.
this one helps explain. before, the level considered unhealthful was way higher than now. thus, the number of days have decreased.

C. In early 2012, a new and far more accurate gas spectrometer was invented.
so what? does it explain why the number of days has dropped?

D. In 2011, the mayor of Los Bernardinos was found to have accepted large campaign donations from local industries and to have exempted those same industries from air pollution control measures.
now this is interesting, in 2011 people found out that some industries were not actually reducing the pollution. after everything came out to public, the pollution decreased, and thus we can explain why in 2012 the number of days decreased.

E. Excess ozone and carbon monoxide (some of the air pollution particulates measured) require a minimum of two years to break down naturally in the atmosphere above a given area.
this one help explain as well, although might not, from the first look. we are told that in 2010, the city adopted some measures. if the measures were successful, but the ozone and carbon monoxide takes time to decompose, then of course, in 2010 and 2011 the number of days with high level of smog were high, and in 2012 dropped considerably.

confused about C - if it was more accurate, it could be reading more correctly now - this could mean that earlier it was raising false alerts.. so how can C least explain the paradox? It certainly can go both ways.

If the meter was inaccurate before, it could be reading incorrectly and raising unnecessary false alerts?

(E) Excess ozone and carbon monoxide (some of the air pollution particulates measured) require a minimum of two years to break down naturally in the atmosphere above a given area.

(E) says after 2 yrs the particles are break down helps to reduce but the release of ozone in every year could be same compensating what ever has been break down that year. No where it mentioned that the release of ozone is reducing year on year.
Means the levels of ozone or pollutants released are same every year and every year the break down is also normal so there is no increase or decrease.

Why cannot this be least one could explain the decrease of pollutants.

Please help me to correct my thought process

Yes, you have a point. Any reduction in pollutants should immediately reflect on the atmosphere, even though the pollutants may take 2 years or any period of time to break down since the cycle of pollutant addition and breaking down occurs continuously. Hence option E also does not help explain the pollutant level.

All the answers can explain the drop in 2012. However, the question is “which would be the LEAST helpful"

A. Explains

B. The scale could be very different in 2012. Explains

C. The premise does not say that the older gas spectrometer was very inaccurate, just that the new one is more accurate. The drop is too steep to be blamed for the accuracy of the spectrometer. Even if the new gas spectrometer could explain some drop, it is the least helpful.

D. When the mayor of Los Bernardinos was found to have accepted donations (He was stopped, so in 2012 those industries were not exempted.) Explains

E. Explains

Answer is C

Option C:
If an accurate* detector was invented in 2012, then the number of alarms should have INCREASED (not decreased) in 2012. However the passage states that the number of smog alerts in Los Bernardinos dropped to 118. Thus invention of detector DOES NOT EXPLAIN the trend seen during the period. Hence Option C is the correct answer.

(*N.B.: Technically, the wording should have been "more sensitive", not "more accurate". Sensitivity of an instrument causes more number of true alarms that are not possible to detect by a less sensitive instrument. Accuracy of an instrument has nothing to do with more number of alarms.)

Dear experts,

The Question stem asks 'Which choice will explain LEAST the trend of measurements in the City from 2009-2012?'.

Option C says, An accurate instrument was invented in 2012.
This choice is very attractive. Can we go that far to conclude to the earlier readings of 128,153, and 160 were not accurate?
We cannot question the premises, but can we doubt about the accuracy?
In that case, The reading of 2012 is correct and explains the sudden drop.

Option D.
It tells about bribe case in 2011. So what exactly to interpret? In that case, the sudden drop in 2012 is effect of bribe of 2011?
And if yes, then why not to assume that the case was exposed in 2011 and it ended then only? I am not sure about my reasoning of Option D.

Please also elaborate on Option C.

Correct answer must explain why the pollution level went up in 2011 and then dropped in 2012.

Option D indicates that some industries were exempted - this may result in a rise in pollutants in the air because these industries might no longer bother to control their emissions. So the rise in pollutants may be explained by this event, but not the drop. Thus D is NOT an explanation and hence could be a correct answer.

On the other hand, an invention of a more sensitive instrument may explain the rise in number of smog alert days recorded, but again this does not explain the subsequent drop.

Moreover, E could also be a possible answer as discussed above (i.e. it cannot explain the rise and then drop in pollution levels).

In my opinion, there is a problem with the question.

I think avinashrao9 is on the money... (C) In early 2012, a new and far more accurate gas spectrometer was invented. The catch here is that the spectrometer was invented but does not mention whether the city has used the same or not

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