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雅思考试阅读测试经典模拟题

发布时间：2006-06-21 23:27 点击：

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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.

　　One theory that seems to fit the facts concerns the depletion of the ozone layer, a well documented phenomenon which has led to a sharp increase in ultraviolet radiation levels.The ozone layer is meant to shield the Earth from UV rays, but increased radiation may be having a greater effect upon frog populations than previously believed. Another theory is that worldwide temperature increases are upsetting the breeding cycles of frogs.

TRUE／FALSE／NOT GIVEN

1.Frogs are disappearing only from city areas.

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