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.
(A) Since the measures weren't implemented in '86-'88, that would explain the continued increase of high pollution days.
(B) This is the tricky and tempting answer, but IMHO a wrong one. The new equipment may be an adequate explanation which suggests that previous figures of pollution were overestimated due to inaccurate measures of inadequate equipment. Let's see if there is another explanation that is worse than this one.
(C) This is a pretty clear-cut explanation - what used to be considered "high pollution level" is now "normal".
(E) This is also a pretty clear-cut scientific explanation - pollutants take time to breakdown, so even if better controls were implemented, damage mitigation will not be immediately apparent.
(D) This is my choice. IMHO, this explanation isn't direct enough and it leaves us having to assume too much (i.e. we must assume that some action was taken to reverse the mayor's policies after the campaign donations scandal). This is by far the worst explanation of the bunch.