The golden toad of Costa Rica, whose beauty and rarity

Hi,

On this question:
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The golden toad of Costa Rica, whose beauty and rarity inspired an unusual degree of human interest from a public generally unconcerned about amphibians, may nevertheless have been driven to extinction by human activity. In the United States, a public relations campaign raised money to protect the toad???s habitat in Costa Rica, establishing the Monteverde Cloud Forest Preserve in 1972. However, setting aside habitat was not enough to save the species. The toad's demise in the late 1980s was a harbinger of further species extinction in Costa Rica. Since that time, another twenty of the fifty species of frogs and toads known to once inhabit a 30 square kilometer area near Monteverde have disappeared.
Between one third and one half of the world???s amphibian species???including frogs, toads, and salamanders???have declined or disappeared. Scientists hypothesize that the more subtle effects of human activities on the world's ecosystems, such as the accretion of pollutants, the decrease in atmospheric ozone, and changing weather patterns due to global warming, are beginning to take their toll. Perhaps amphibians - whose permeable skin makes them unusually sensitive to environmental changes - are the biological harbingers of the natural world, giving humans early notification of the deterioration, if not destruction, of our ecosystem.


It can be inferred from the discussion of amphibians that
A only thirty species of frogs and toads remain in Costa Rica
B relatively few non-amphibious animals have permeable skin
C most have either already become extinct or are in danger of extinction
D humans do not usually take signals of environmental deterioration seriously
E the extinction of so many amphibian species supports the contention that humans are responsible for the situation
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The OA is B. I chose E (which actually didn't really convince me 100%, but I eliminated all others). I eliminated B because it implies, by saying few, that there are non-amphibious animals that have permeable skin, but we can't infer that from the text. There may or may not be any. I agree that we can infer that it is a rare characteristic, but it could be that no other animal has permeable skin, we just don't know, that's why I think it can't be correct.

I would appreciate your help on this question.

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