Aboutacenturyago,theaveragelife-span(寿命)forAmericanswas...

问题详情：

About a century ago, the average life-span (寿命) 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（制冷技术）and sewage treatment

（污水处理） meant  that  young  people  were  able  to  survive  longer.  Moreover,  medical

breakthroughs helped contain diseases such as polio（小儿麻痹症）, 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(假设) highly unlikely. Our bodies’ cells can keep reproducing for only so long before they peter out（*）. 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.

ared with the average life-span about a century ago, the typical American lives about

r World War II, the longer average life spans mainly resulted from________. igeration and sewage treatment

cal breakthroughs ing the cells dividing longer cing polio

is the scientists’ attitude towards the view “we have reached our life-span limit”?

ortive                       ctive               C. optimistic                   pproving

rding to some life-expectancy researchers, keeping our bodies’ cells reproducing before they peter out may be________.

ssible                       B. possible                C. exciting                    erning

【回答】

CBDA

知识点：科普环保类阅读

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