Saving the Earth
The population of the earth is increasing very fast. Humans must make the earth support the increasing population. This has made it necessary for agriculture and industry to develop rapidly. Such a rapid development produces more and more waste, which goes into the water, the soil and the air. Some of it is made harmless. However, where there is too much of it, the poisonous waste may do great harm to the things around the people.
When farmers add fertilizer to the soil to make plants grow better, or use poison to kill pests, poison is sent into the air, the water and the soil. When birds, fish and people eat the grain, drink the water or breath the air, harm will be done to their health.
The air in big cities is often made very dirty by cars and factories. Millions of tons of waste and poisonous gases are sent into the air with the smoke. In some places, little is done to make the smoke clean before it goes into the air.
Fortunately, people are beginning to realize just how serious the whole situation is. In many countries, laws have been made to stop factories from sending out poisonous gases.
[点评]
人类人口过快的增长，社会过快的发展使地球不堪重负。所幸，人们已意识到这一点，开始行动起来拯救地球，也就是拯救自己。此文证据虽然充分，结尾却有些分量不足。
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拯救地球
地球的人口增长很快。人类要使地球能够养活众多的人口，就得迅速发展工农业。由于工农业的迅速发展，即能产生出越来越多的废弃物，这些废弃物流进水里，渗入到土壤中，散发进空气中。其中的有些是无害的。然而，在废弃物太多的地方，有毒的东西会对周围的物和人有害。
农民为了让庄稼地茂盛，给地里施肥，为了杀死害虫，往地里喷药，这个时候，有毒的气体就会散发到空气中，水里和上壤里。当鸟、鱼以及人们吃这些粮食，饮用这些水，呼吸空气时，就对他们的健康造成危害。
大城市的空气经常被汽车和工厂弄得很糟。成千上万吨的废物和有毒气体随烟散发到空气中，有些地方，根本就不做净化处理，直接让它排到空气中。
可庆幸的是，人们已渐渐对此严重的形势有所认识。有些国家还颁布了法令来阻止工厂向外排放毒气。