职称英语理工类阅读理解复习必备练习题(3)

　　In the 1980s, scientists around the world began to notice something strange: Frogs were disappearing. More recent research has shown that many kinds of amphibians are declining or have become extinct. They have been around for a long time - over 350 million years. Why are they dying out now? 　　The most serious aspect of amphibian loss, however, goes beyond the amphibians themselves. Scientists are beginning to think about what amphibian decline means for the planet as a whole. If the earth is becoming unlivable for amphibians, is it also becoming unlivable for other kinds of animals and human beings as well? 　　There are a number of other factors in amphibian decline. Pollution is one of them. In many industrial areas, air pollution has poisoned the rain, which then falls on ponds and kills the frogs and toads that live there. In farming areas, the heavy use of chemicals on crops has also killed off amphibians. Another factor is that air pollution has led to increased levels of ultraviolet light. This endangers amphibians, which seem to be especially sensitive to UV light. And finally, scientists have discovered a new disease that seems to be killing many species of amphibians in different parts of the world. 　　36 Losing amphibians means losing 　　B knowledge about air and water pollution. 　　D an opportunity to detect poisonous gases. 　　A in any stream they can find, 　　C only on sand. 　　38 The arroyo toad is disappearing because 　　B it is losing its habitat. 　　D it cant bear the cold of winter. 　　A poisonous gases. 　　C water leakage. 　　40 Scientists think that the decline of amphibians could 　　B cause a decline in other kinds of animals. 　　D be a good sign for human beings.