2017年职称英语《理工B类》考试阅读判断练习题(8)

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2017年03月13日

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　　This November, a hundred million butterflies will drop from the sky over Mexico, like autumn leaves. But for how long? Genetically modified maize (玉米) could mean extinction for this beautiful butterfly, Rafael Ruiz reports.

　　Although its body is about 3 cm long and it only weighs 1 gin, the Monarch butterfly manages to travel 5,000 km each year. It seems to be so fragile, but its long journeys are proof of its amazing ability to survive. This autumn, the Monarch butterfly will once more set out on its journey from the US. It will keep going until it reaches Mexico. It travels these huge distances to escape the cold weather in the north.

　　In November, millions of Monarchs fall like bright, golden rain onto the forests in the mountains of central Mexico. In the silence of these mountains you can hear a strange flapping (拍动) of wings, as the Monarchs arrive at their destination. In the mountains, which reach a height of 3,000 metres, the butterflies are safe.

　　Before reaching their journey's end they have faced strong winds, rain and snowstorms and they do not all manage to reach their destination. When the winters are really bad, perhaps 70 per cent of them will not survive. Their long journey to Mexico is thought to be one of the most amazing events in the whole of the American continent. When they get there they will stay until the beginning of April, when their internal calendar tells them that it is time to go back. The long journey, with all its dangers, begins again.

　　These delicate creatures now face danger of another kind - from scientific progress. In the US, millions of farms grow genetically modified maize which is pure poison for the butterfly. Laboratory experiments have shown that half of the butterflies which feed on the leaves of genetically modified maize die within 48 hours. Not all experts agree that this variety of maize is responsible for the threat to the Monarchs. In spite of these doubts, the European Union has refused to approve new crops of genetically modified maize until further investigations have been carried out.

　　Greenpeace is campaigning against genetically modified products (in Spain, there are already 20,000 hectares of modified maize). The environmental organization recently published a list of 100 species of butterfly in Europe alone which are threatened with extinction.

　　16 The Monarch butterfly travels 5,000 km each year.