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山西省2017高考英语二轮复习专题训练：阅读理解（25） 阅读下面短文，从短文后所给各题的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项。 A Scientific experiments can sometimes go wrong and when they do the results may range from the disastrous to the troubling. One such experiment took place in South America about fifty years ago. Whether its final consequences will cause serious damage or nothing more than a small trouble still remains to be seen. The story began in 1956 when an American scientist working in Brazil decided to solve the problem of increasing the productivity of that country's bees. He imported a very active type of African bee from Tanzania and mated it with the more easy-going native variety to produce a new kind of bees. The new bees worked harder and produced twice as much honey. It seemed that Professor Kerr, for that was the scientist's name, had a total success on his hands. Then things began to go wrong. For some reason as yet unseen, but perhaps as a result of something in their environment, the new bees began to develop extremely attacking personalities. They became bad-tempered and easy to be angry, attacked the native bees and drove them from their living places. But worse was to follow. Having taken over the countryside, the new bees, with their dangerous stings (叮), began to attack its neighbours — cats, dogs, horses, chickens and finally man himself. A long period of terror began that has so far killed a great number of animals and about 150 human beings. | 
