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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

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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.
The author wrote the article to______.
选项 A、explain the current situation of frog extinction
B、elaborate the reasons why frogs are dying out
C、warn people about the environment crisis
D、report a latest study
答案A
解析 主旨题。这道题考查的是对文章大意的掌握。本文讲述的是青蛙灭绝的现象，用了很．大篇幅介绍了澳大利亚现在所面临的实际情况，第二段则举例介绍了一种灭绝的青蛙，最后以现在灭绝物种的种类数量来结尾。文中既没有说青蛙灭绝的原因，也没有警告人们生态危机，也没有介绍最新的研究，只是介绍了一下灭绝的现象。故选A。
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