Research findings from Norwegian and Danish scientists released in late 1997 indicate that the world’s reindeer are "hot" — radi

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问题    Research findings from Norwegian and Danish scientists released in late 1997 indicate that the world’s reindeer are "hot" — radioactive — and are contaminating their owners and minders.
   The radiation comes as a result of the 500 atomic bomb tests carried out in the atmosphere by the nuclear nations in the 1950s and 1960s. Long-lived isotopes in the fall-out have built up in Arctic lichens which are the reindeer’s staple diet. The reindeer have been found to concentrate the isotopes in their bodies. Animals are affected all over the Arctic, with the most radioactive reindeer in Canada, Alaska and Siberia’s Taimyr Peninsula.
   Enormous amounts of reindeer meat — some 14,000 tonnes — are eaten in the Arctic each year. Research at the Danish Riso National Laboratory has found that reindeer herders, who consume a lot of the meat, take in 300 times more radiation each year than is the average anywhere in northern Europe. Norway’s Radiation Protection Authority estimates that many hundreds of herders have died of cancer as a result.
   Meanwhile reindeer are emerging as one of the greatest environmental threats to the Norwegian Arctic. Over-grazing and trampling is causing more damage to the fragile tundra than pollutants from the world’s worst-offending factories. Over the last 40 years the number of reindeer in the Norwegian Arctic have doubled, reaching 20 animals per square kilometre, a very high density. Research by the Norwegian and Danish geological surveys and Russia’s Kola Science Centre have found that 75 percent of the moss in the Norwegian Arctic and 85 percent of lichen have been "severely damaged" by reindeer. Three-quarters of the area is suffering from soil erosion. By contrast, two of the world’s most polluting factories---nickel smelters in Russia’s Kola peninsula — have about 10 percent of the moss and 14 percent of the lichen in the area.
   Even the Saami people, who own most of the reindeer, admit that the animals may be causing problems. Lars-Ander Baer, vice-president of their council, admitted to a conference on the Arctic environment recently: "We simply don’t know how many reindeer the northern part of Norway can take."
Which of the following is NOT a cause of the problem under discussion?

选项 A、Over-grazing.
B、Radioactive contamination.
C、Poaching.
D、Trampling.

答案C

解析
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