My pre-phrase on this question led me to the correct choice but then I found a problem. The choice is saying animals have been saved due to the establishment of "animal refuges." In order for this choice to weaken the argument we must take "animal refuges" to mean basically creating a refuge within an animal's natural habitat. However, it's obvious that "animal refuge" could also mean something set up for endangered animals outside of their natural environment. If it means the latter then the choice would be just like choice E and would not at all weaken the argument.
On the other hand, choice A suggests that at the current point in time the preservation of habitats is more possible than ever before. Given the potential fault of choice B, I actually went with this choice because it suggests that the previous record of increased rate of extinction may in fact be dented (or some positive results could happen), and thus the efforts today wouldn't be a waste, if there is an advance in the protection of habitats. It would be a very weak strengthener--it would need more steps to strongly strengthen the argument, but sometimes correct strengtheners are fairly weak, especially if a more attractive answer choice is flawed.
After all, it could mean that before, and during the increased efforts to protect the natural habitats, the preservation of the habitats was fairly impossible, and now, learning that scientists have better methods than ever before, it could be a thousand times better, and could have far reaching effects on the rate of extinction. That's left open by the answer choice. Again, it could be that the increase was tiny and that therefore this answer choice has no effect, but there's at least a chance for an effect.
Trust me, I pre-phrased the clear flaw here--just because the rate of extinction goes up certainly doesn't mean the "efforts are wasted." Clearly the correct choice will say that some species have been saved by protecting natural habitats--so even with an increasing rate the efforts aren't a waste because it's making some sort of dent. But again, as the test makers have done many times, they tried to make things a little more difficult by swapping terms, and an "animal refuge" by no means has to be in the animals' natural habitat. "Protecting natural habitats" and establishing "animal refuges" is a poor match. That sort of poor match could be exploited in a question at a higher level of difficulty, so why do the test makers feel fine inserting it into a question at a lower level of difficulty? What is the best way to avoid messing up on questions like this? Should one not be careful to precisely divide between terms on easy questions, but try getting more careful where there may be harder questions?
A necessary assumption question could easily be like this:
"The rate of extinction among endangered species is growing higher every year, and these species are an important part of the Earth. The best way to lower the rate of extinction is by protecting the species' natural environments. Therefore, if we want to take the most ideal route, we ought to establish wildlife refuges."
Correct answer choice:
"At least some wildlife refuges protect species natural environments"
By no means is it a given that "wildlife refuges" means natural environments. So what should we do in a situation like this? Should we try not to be precise? Should we not try to avoid making any assumptions?