Critical Reasoning

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.

in 1988,number of alert days is reduced.this mean level of pollution is lower.

all choice except D can explain this lower level. D is correct.

in this causal relation is used.

IMO D

I would go for B.

'B' seems to provide least help. It says in 1988 far more accurate gas spectrometer was invented. The question here is "was it ever used" therefore you can conclude that this statement does not help to evaluate the argument.

On the other hand, 'D' clearly points out the reason of high level of smog in 1988.

u r right man!!!

By oversight I opted a wrong option .As u said D actually helps is supporting the arg.

Whereas B says that new instrument has been invented only.Whether it is applied in day today use for monitoring or not is not mentioned.So on that note B is valid.

Thanks bro!!
B is a valid option
!!

D is such a trap.
B it is!

Indians always say CAT is tougher that GMAT. I have gone thru the papers.To some extent Quants are tough.

But GMAT is also tuf on its own way...

I believe the answer should be D