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  3. The Earth has been stripped of up to 90% of its species five times before in the past 450 million years. Now it’s about to happe

The Earth has been stripped of up to 90% of its species five times before in the past 450 million years. Now it’s about to happe

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问题     The Earth has been stripped of up to 90% of its species five times before in the past 450 million years. Now it’s about to happen again—and this time there’s no rogue asteroid(小行星)to blame. One of the first great rules of terrestrial biology is that no species is forever. The Earth has gone through five major extinction events before. The result of all of the extinctions was the same: death, a lot of it.
    As increasingly accepted theories have argued—and as the Science papers show— we are now in the midst of the sixth great extinction, the unsettlingly-named Anthropocene(人类纪), or the age of the humans.
    As the authors of all this loss, we are doing our nasty work in a lot of ways. Overexploitation—which is to say killing animals for food, clothing or the sheer perverse pleasure of it—plays a big role. So we get elephants slaughtered for their tusks, rhinos poached(偷猎)for their horns and tigers shot and skinned for their pelts, until oops— no more elephants, rhinos or tigers.
    Habitat destruction is another big driver, particularly in rainforests. And you don’ t even have to chop or burn an ecosystem completely away to threaten its species; sometimes all it takes is cutting a few roads across it or building a few farms or homes in the wrong spots.
    Then too there is global warming, which makes once-hospitable habitats too hot or dry or stormy for species adapted to different conditions. Finally, as TIME’s Bryan Walsh wrote in last week’ s cover story, there are invasive species—pests like the giant African snail, the lionfish—which hitch a ride into a new ecosystem on ships or packing material, or are brought in as pets, and then reproduce wildly, crowding out native species.
    It oughtn’ t to take appealing to our self-interest to get us to quit making such a mess of what we ’re increasingly coming to learn is an exceedingly destructible world. But it’ s that very self-interest that led us to make that mess in the first place. We can either start to change our ways, or we can keep going the way we are—at least until the Anthropocene extinction claims one final species: our own.
The first sentence in the first paragraph doesn’ t indicate that______.
选项 A、the species on earth have decreased 90% now
B、the past 450 million years have witnessed extinction several times
C、every extinction has a 90% species decrease
D、the earth has experienced five great extinction
答案A
解析 细节题。“The Earth has been stripped of up to 90％ of its species five timesbefore in the past 450 million years”意为在过去的4．5亿年中，地球曾经五次损失了90％的生物。A中错在不是现在，而是在过去的4．5亿年。B、C、D都符合文意。本题考察的是对成分复杂句子的解读。
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大学英语四级

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