Some people imagine leave this fearful world， only to come down to earth. Scientists tell us that of all the stars known in the vast universe， the earth is the only planet on which human beings can survive. But now we are facing the risky problems concerning our existence on earth.
    Worldwide environmental deterioration （惡化） is alarming. The earth is plagued with population explosion， energy crisis， lacked of food， housing problem and environmental pollution. During the process of industrialization， human beings are pursuing crazily the benefits from the economic growth. Now we have suffered from the results. The overuse of natural resources has affected ecosystem（生態(tài)系統(tǒng)） on earth.
    These seem to be some of the ways in which our common home is under destruction. The quality of our lives has enormously deteriorated in many aspects. Now our planet is experiencing survival tensions. Only when all of us make consistent efforts can we preserve the environment on earth， because there is no another earth in universe.
    核心剖析 結(jié)尾回到文章開頭闡明的中心思想或主題句上，使首尾遙相呼應(yīng)。這樣處理增強(qiáng)了語言表達(dá)力度，從而達(dá)到再次肯定和強(qiáng)調(diào)的效果。（注意：不要為結(jié)束而單純地重復(fù)開始段的話。）