16.About a century ago,the average life-span (壽命) for Americans was about 50 years.Today,the typical American lives for around seventy-eight years.
According to a German aging study,the maximum life span in industrialized countries has increased by two years every decade since the mid 19th century.What accounts for such increased longevity?Between 1900 and 1950,inventions such as refrigeration(制冷技術)and sewage treatment(污水處理) meant that young people were able to survive longer.Moreover,medical breakthroughs helped contain diseases such as polio(小兒麻痹癥),which killed many children.These advances helped increase the average life span.
Medical discoveries after World War II tended to benefit older people.Treatments for heart disease,for example,have allowed the elderly to live longer on average.So does this mean that future medical breakthroughs will result in even longer average life spans,or have we reached our limit?Scientists disagree.
Some argue that if science is one day able to remove disease and old-age infirmity,there will be virtually no limit on how long humans can live.Some even predict that by the year 2150,the average life span will have increased to around 120 years.
Other life-expectancy researchers find that scenario(假設) highly unlikely.Our bodies'cells can keep reproducing for only so long before they peter out(分裂).Only when science finds a way to keep our cells dividing longer will we see another significant leap in life expectancy.
Still,with plenty of exercise and a healthy diet,those who hold the view can always hope that they'll live long enough to break the record held by Jeanne Louise Calment of France,who lived to be 122.
28.Compared with the average life-span about a century ago,the typical American lives about
C years longer at present.
A.50
B.78
C.28
D.42
29.After World War II,the longer average life spans mainly resulted fromB.
A.refrigeration and sewage treatment
B.medical breakthroughs
C.keeping the cells dividing longer
D.reducing polio
30.What is the scientists'attitude towards the view"we have reached our life-span limit"?D
A.supportive
B.objective
C.optimistic
D.disapproving
31.According to some life-expectancy researchers,keeping our bodies'cells reproducing before they peter out may beA.
A.impossible
B.possible
C.exciting
D.concerning.
分析 本文是一篇科教類閱讀,屬于說明文,大約一個世紀前,美國人的平均壽命約為五十年.今天,典型的美國人的壽命約七十八年.本文以此展開討論,主要講述了不同時期人們的平均壽命增加的原因.
解答 28.C.細節(jié)理解題.根據About a century ago,the average life-span (壽命) for Americans was about 50 years.Today,the typical American lives for around seventy-eight years.可知,一個世紀前,平均壽命是50,現在是78.故現在比原來長28.故選C.
29.B.細節(jié)理解題.根據Medical discoveries after World War II tended to benefit older people.可知,在世界第二次大戰(zhàn)期間是醫(yī)學突破有利于人們的壽命.故選B.
30.D.推理判斷題.根據So does this mean that future medical breakthroughs will result in even longer average life spans,or have we reached our limit?Scientists disagree.可知,作者對于我們已經達到了壽命極限是不支持.故選D.
31.A.細節(jié)理解題.根據Other life-expectancy researchers find that scenario(假設) highly unlikely.Our bodies'cells can keep reproducing for only so long before they peter out(分裂).Only when science finds a way to keep our cells dividing longer will we see another significant leap in life expectancy.可知,其他預期壽命的研究人員發(fā)現,假設非常不可能.我們的身體細胞只有在分裂之前才能保持繁殖.只有當科學找到一種保持細胞分裂更長時間的方式,我們才會看到另一個重要的飛躍預期壽命.故選A.
點評 本文是一篇科教類閱讀,題目涉及多道主旨大意題,細節(jié)理解題,推理判斷題.做題時學生應仔細閱讀原文,把握文章主要內容,聯(lián)系文章上下文內容并結合所給選項含義,從中選出正確答案,一定要做到有理有據,切忌胡亂猜測.