问答题 Listen to the following passage. Altogether the passage will be read to you four times. During the first reading, which will be done at normal speed, listen and try to understand the meaning. For the second and third readings, the passage will be read sentence by sentence, or phrase by phrase, with intervals of 15 seconds. The last reading will be done at normal speed again and during this time you should check your work. You will then be given 1 minute to check through your work once more.
Please write the whole passage on ANSWER SHEET ONE.
【正确答案】
【答案解析】[听力原文]
Life Span

About a century, ago, the average life span for Americans was about 50 years. /Today, the typical American lives for around seventy-eight years. / What accounts for such increased longevity? /Between 1900 and 1950, inventions such as refrigeration and sewage treatment meant that/young people were able to survive longer. /Moreover, medical breakthroughs helped contain diseases/such as some fatal ones that killed many children. /These advances helped increase the average life span. /This means that future medical breakthroughs will result in even longer average life span.