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Nobody likes insects. They are annoying and sometimes dangerous. Some of them bite us and give us 51 ; others bite us and give us big red 52 . Some do not bite, 53 they just fly round our heads or crawl round our houses and gardens. And we do not like any of them 54 those lovely butterflies. But insects are interesting. First, they are very 55 animals. Three hundred and twenty million years ago there were no men or other mammals in the world but there were insects. Today, 56 every square mile of land there are millions of them flying and crawling 57 . Second, insects are very adaptable to their habitat, to their food and to the weather. Now there are about a million different 58 in the world. 59 do people use insecticides? Not many insects 60 us. In many cases we do not see the insects and we do not think much about them. The reason is that insects eat 61 of mans food, 62 there are so many billions of them. We must use insecticides to get rid of them. An insecticide is simply a special chemical 63 with some poisonous elements. Farmers spray their crops very often and the insects die quickly. Of course some poisonous chemicals may 64 on the crops or in the 65 , and that is also dangerous. 51. A. wounds B. diseases C. disturbance D. panic 52. A. places B. points C. spots D. stains 53. A. because B. but C. or D. while | 
