题干

呼伦贝尔草原是我国最大的牧业基地,过去那里有许多狼,对牧业的发展构成严重的威胁,所以当地牧民曾组织过大规模的猎捕狼的活动.但随后兔以惊人的速度发展起来,兔与牛羊争食牧草,加速了草场的退化.通过以上资料分析,你认为人类____随意灭杀某种动物,因为生态系统中各种生物之间存在着相互依赖和相互____的关系,使得各种生物的____和所占的比例总是维持在相对稳定的状态,即生态平衡.
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不能,制约,数量

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先阅读短文,然后根据短文内容从方框内所给的单词中选择恰当的词(注意词形变化)填入短文空白处,使短文完整、通顺。一词只用一次,一空限填一词。方框中有两个词是多余的。将能填入空白处的答案写在答题卡上的相应题号后。

   The world itself is becoming much smaller by using modern traffic and modern communication. Life today is much ____  than it was hundreds of years ago, but it has brought new problems. One of the biggest is ____ . To pollute means to make things dirty. Pollution comes in many ways. We see it, drink it and even hear it.
   Man has been polluting the earth. The more people are, the more pollution is. Many years ago, the problem was not so  ____  because there were not so many people. When the land was ____   up or the river was dirty in a place, men moved to another one. But this is no ____   true. Man is now slowly pollution the ____  world.
   Air pollution is still the most serious. It’s bad to all living things in the world, but it is not ____ one kind of pollution. Water pollution ____  our fish and pollutes our drinking water. Noise pollution makes us become angry more easily.
   Many countries are making rules to ____  pollution. They stop the people from burning coal in houses and factories in the city, and from blowing dirty smoke into the air. The pollution of SO2 is now the most dangerous problem of air pollution. It is caused by heavy traffic. It is certain that if there are fewer people driving, there will be ____  air pollution.
   The earth is our home. We must take care of it. That means ____  the land, water and air clean.