Critical Reasoning

Weighing in at roughly one ton of whiskers, flippers, blubber, and bone each, Stellers are the largest and most northerly of all sea lions. Many spend the summers on Alaska's Chiswell Island resting, battling, breeding, and feeding. Stellars have suffered a mysterious population decline of about two-thirds since the 1960s, most likely due to pollution, disease, and competition for food from commercial fishing. Stellers should be considered an endangered species and thus be protected.

Which of the following, if true, indicates a flaw in the reasoning above?

A. Stellers are not a popular animal among the zoo-visiting population and, therefore, are not worth saving.
B. It would take too many resources to save animals as big as Stellers.
C. There is no proof that the decline in population among Stellers is due to outside dangers.
D. A species must suffer population declines of 90% or more to be put on the endangered species list.
E. Endangered species sometimes die out anyway.





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[spoiler]Answer: D[/spoiler]

Can anyone explain about the choice C for me? I was looking for an alternative reason to weaken this argument, so if there are other reasons than environmental pollution and feeding, the choice will weaken the conclusion, doesn't it?

Thanks

IMO D. D states the requirement of putting a species into endangered zone .And sea lion lacks that .

C says outside dangers , whereas reasons for reduction in number is well stated in the argument " pollution, disease, and competition for food from commercial fishing".So eliminate C.

Here the conclusion is: Stellars must be put on endangered list.

Premises: decline of 2/3 population.
Stellar size.
Rest in Alaska
mysterious decline etc.


How do we weaken the conclusion that they are to be put on endangered list? By proving that they dont satisfy the criteria to be called
endangered.

A: Zoo-visits are out of scope.
B: Amt of resources also not discussed
C: Outside the scope of the argument. It is saying that there is no proof that the decline is due to outside dangers. It does not mean that it is not endangered. However it is endangered, it is endangered.
D: To be endangered, you need 90% decline but decline is only 2/3 which is ~ 67%. So this directly weakens the conclusion that the species is to be marked endangered.
E: No reason not to try and protect!

The Argument also mentions internal causes such as diseases, hence C is not the correct choice

What About E ?
Even if the Sea Lions were to die inspite of being declaraed an Endangered species, wouldnt the argument be weakened.