Một trường tiểu học có 567 học sinh ,số học sinh nam bằng2/5 số học sinh nữ .Hỏi trường đó có bao nhiêu học sinh nam học sinh nữ?

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biodiversity conservation consumption erosion exhaust exploitation fertilizer food chain genetically modified hydroelectric pesticide rechargeable renewable residues wind turbine 42. Poisons which are used on one species can enter the .................................... and affect other species. 43. A chemical ............................................. may destroy harmful insects, but it often has undesirable side-effects. 44. A great deal of ............................................. is used to increase the yield of crops. But it then runs 45. Your car ............................................. may look OK, but in fact it is part of the biggest and fastest growing global source of pollution. 46. It is important to preserve as many species of plant and animal as we can, to maintain ............................................. 47. Most of the wildlife of a country like Britain has long been destroyed. The priority now is the ............................................. of what remains. 48. Conservationists are very suspicious of ............................................. crops; they fear “genetic pollution” of other species. 49. A ............................................. produces totally clean energy. But some people think they are too big, noisy and ugly. 50. Oil can only be used once, whereas ............................................. sources of energy like wind and the sun go on for ever. 51. The use of ............................................. batteries, for example in personal stereos, helps to reduce waste and pollution. 52. The ............................................. of energy is very high in the rich, developed countries. 53. In many places the destruction of forest has lead to serious ............................................. of the soil, and sometimes to flooding.