题目材料
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.
In the second paragraph, the author notes that amphibians have permeable skin in order to
- Aargue that the golden toad is not the only endangered amphibian
- Bexplain why amphibians might be affected earlier than other animals by an adverse environment
- Cillustrate that preserving the golden toad`s habitat was not enough to save the species
- Ddemonstrate that the accretion of pollutants poses a greater threat to amphibian species than do changes to the atmosphere or climate
- Esuggest that threats to amphibians need not be a cause for human concern
显示答案
正确答案: B