noboru wrote:
A distemper virus has caused two-thirds of the seal population in the North Sea to die since May 1988. The explanation for the deaths cannot rest here, however. There must be a reason the normally latent virus could prevail so suddenly: clearly the severe pollution of the North Sea waters must have weakened the immune system of the seals so that they could no longer withstand the virus.
Which one of the following, if true, most strongly supports the explanation given in the argument?
(A) At various times during the last ten years, several species of shellfish and seabirds in the North Sea have experienced unprecedented steep drops in population.
(B) By reducing pollution at its source, Northern Europe and Scandinavia have been taking the lead in preventing pollution from reaching the waters of the North Sea.
(C) For many years, fish for human consumption have been taken from the waters of the North Sea.
(D) There are two species of seal found throughout the North Sea area, the common seal and the gray seal.
(E) The distemper caused by the virus was a disease that was new to the population of North Sea seals in May 1988, and so the seals’ immune systems were unprepared to counter it.
Same passage with different stem question:
LINKOfficial Explanation
(A) Yes. Since presumably the distemper virus that affects seals would not affect such disparate animals as shellfish and seabirds, it is likely that another agent caused all three populations to decrease—pollution.
(B) No. This would weaken the argument. If pollution is being reduced, then pollution is less likely now to be the cause of the weakening of the seals’ immune system than in the past.
(C) No. We don’t know how this has affected the immune system of humans. If humans are becoming more susceptible to similar viruses, then it would support the argument. However, if humans are not becoming more susceptible to similar viruses, then it would weaken the argument.
(D) No. This is irrelevant. The passage is about the general population of seals. We don’t need to know the distribution of the various species.
(E) No. This would weaken the argument. If the seals’ immune system were unprepared for the new strain of virus, then the spread of the virus probably would have occurred even without the pollution