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  3. When was the last time you saw a frog? Chances are, if you live in a city, you have not seen one for some time. Even in wet area

When was the last time you saw a frog? Chances are, if you live in a city, you have not seen one for some time. Even in wet area

admin2014-12-31  23
问题     When was the last time you saw a frog? Chances are, if you live in a city, you have not seen one for some time. Even in wet areas once teeming with frogs and toads, it is becoming less and less easy to find those slimy, hopping and sometimes poisonous members of the animal kingdom. All over the world, and even in remote parts of Australia, frogs are losing the ecological battle for survival, and biologists are at a loss to explain their demise. Are amphibians(两栖动物)simply oversensitive to changes in the ecosystem? Could it be that their rapid decline in numbers is signaling some coming environmental disaster for us all? This frightening scenario is in part the consequence of a dramatic increase over the last quarter century in the development of once natural areas of wet marshland-home not only to frogs but to all manner of wildlife. However, as yet, there are no obvious reasons why certain frog species are disappearing from rainforests in Australia that have barely been touched by human hand. The mystery is unsettling to say the least, for it is known that amphibian species are extremely sensitive to environmental variations in temperature and moisture levels. The danger is that planet Earth might not only lose a vital link in the ecological food chain(frogs keep populations of otherwise pestilent insects at manageable levels), but we might be increasing our output of air pollutants to levels that may have already become irreversible. Frogs could be inadvertently warning us of a catastrophe.
    An example of a species of frog that, at far as is known, has become extinct, is the platypus(鸭嘴兽)frog. Like the well-known Australian mammal it was named after, it exhibited some very strange behavior; instead of giving birth to tadpoles in the water, it raised its young within its stomach. The baby frogs were actually born from out of their mother’s mouth. Discovered in 1981, less than ten years later the frog had completely vanished from the crystal clear waters of Booloumba Creek near Queensland’s Sunshine Coast. Unfortunately, this freak of nature is not the only frog species to have been lost in Australia. Since the 1970s, no less than eight others have suffered the same fate.
According to the author, which statement is NOT the reason why frog extinction is dangerous?
选项 A、It is a sign that the environment has been polluted badly.
B、They can control the pests at a certain level.
C、It is an important member in the food chain.
D、It brings damage to human beings financially.
答案D
解析 细节题。文章对于青蛙消失所带来的危机的内容集中在第一段后半部分．“The danger is that planet Earth might not only lose a vital link in the ecological foodchain(frogs keep populations of otherwise pestilent insects at manageable levels)，butwe might be increasing our output of air pollutants to levels that may have alreadybecome irreversible．Frogs could be inadvertently warning us of a catastrophe．”它是食物链中重要的一环，可以控制害虫量，还是我们对于环境破坏的警钟，只有D项，在经济上对人类造成损坏没有提及。故选D。
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