geet wrote:A stingray without parasites is healthier than it would be if it had parasites. Nevertheless, the lack of parasites in stingrays is an indicator that the ecosystem in which the stingrays live is under environmental stress such as pollution.
Which one of the following, if true, most helps to reconcile the discrepancy indicated above?
(A) During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which are environmentally vulnerable organisms.
(B) A stingray is a free-ranging predator that feeds on smaller organisms but has few predators itself.
(C) A parasite drains part of the vitality of its host by drawing nourishment from the host.
(D) An ecosystem can be considered stressed if only a few species of very simple organisms can live there.
(E) Since the life of parasites depends on that of their host, they need to live without k!II!ng their host or else to reproduce and infect other individuals before their own host dies.

OA is A...remember to explain the logic!!!

To figure out the answer to this problem, you have to look at the reasoning the author is making for arriving at his conclusion. His conclusion is that if there are no parasites on the sting ray, then it is under environmental stress.

To reconcile his discrepency, we have to prove that environmental stress is indeed the reason why stingrays do not have parasites.

By stating shrimps and oysters are environmentally vulnerable organisms and they are parasites of the sting ray (A), we can provide enough evidence that a stingray without any parasites is living in an "environmentally stressed" situation.

geet wrote: ok,i do understand that if there are no parasites on the stingray, then it will live under environmental stress, but how come pollution came in to play, i mean yes if parasite make shrimps and oysters their host then environment will come under stress but stress of pollution?? i didn't get that!!