Woodco Plywood Manufacturer: Ten years ago a study linked the high rates of respiratory ailments in Loganville to airborne pollutants released in the manufacture of plywood. In response, the city government imposed strict regulations on emissions from our plant, which we have followed at great cost to our production capacity. But after an initial dip, the rate of respiratory ailments rose to new levels, so the high rate was never a result of pollution from our plant.
Which of the following, if true, most seriously weakens the argument?Woodco argues that because respiratory ailments eventually rose again after its emissions were reduced, its pollution was **never responsible for the high ailment rate**. The weak point is that *the later rise could have had a new source*. If so, the initial decline could still show that Woodco’s pollution had contributed to the earlier problem.
(A) Over the last decade, a series of studies linking respiratory ailments to dietary deficiencies has been published.
Incorrect. This provides another possible cause of respiratory ailments, but it does not explain the specific pattern of an initial decline followed by a later rise. It certainly does not show that Woodco’s pollution contributed to the earlier high rate.
(B) Seven years ago, the Woodco plant installed equipment to increase production capacity without increasing annual pollutant emissions.
Incorrect. Since Woodco’s pollutant emissions did not increase, this does not explain why respiratory ailments later rose again.
(C) Pollutant emissions at Woodco plywood plants in other towns have declined during the past twelve years.
Incorrect. The issue is pollution and respiratory ailments in Loganville, so emissions from plants elsewhere are irrelevant.
(D) Nine years ago, a competing plywood manufacturer opened a plant just across the river from Woodco’s plant.
Correct. The timing is crucial. Woodco reduced its emissions ten years ago, after which respiratory ailments initially declined. Then, nine years ago, another plywood plant opened nearby. Pollution from that new plant could explain why respiratory ailments subsequently rose again. Thus, the initial decline may still have resulted from reducing Woodco’s pollution, undermining Woodco’s conclusion that its pollution was **never** responsible.
(E) There are more facilities for treating respiratory ailments in Loganville today than there were eleven years ago.
Incorrect. This tells us only that the number of treatment facilities increased sometime during the period. It does not establish that the additional facilities caused more cases to be detected or reported, or that they appeared at the time when the ailment rate began rising again. Thus, it does not explain the initial decline followed by the later increase.
Answer: (D)