Like distance runners on a measured course，all of us will move through time in a roughly predictable pattern．
In the first stage of our lives，we develop and grow, reaching toward the top of physical vitality(活力)．
After we grow up，however, the body begins a process of gradually wearing out．
A new awareness of physical fitness may help lengthen our years of health and vitality，yet nothing we do will work to stop the unavoidable force of aging．
Most of the changes of aging take place deep inside the body．The lungs become less able to take in oxygen．Powerful muscles gradually lose their strength．The heart loses power and pumps less blood．Bones grow easier to break．
Finally, we meet a stress，a stress that is greater than our physical resistance．Often，it is only a minor accident or chance infection(a disease caused by virus)，but this time，it brings life to an end．
In 1932，a classic experiment nearly doubled the lifetime of rats，simply by cutting back the calories in their diet The reason for the effect was then unknown．
Today, at the University of California at Berkley, Dr．Paul Seagle has also greatly lengthened the normal lifetime of rats．The result was achieved through a special protein limited diet，which had a great effect on the chemistry of the brain．Seagle showed that within the brain，specific chemicals control many of the signals that influence aging．By changing that chemical balance，the clock of aging can be reset．
For the first time, the mystery of why we age is being seriously challenged．Scientists in many fields are now making striking and far-reaching discoveries．
An average lifetime lasts 75 years，yet in each of us lies a potential for a longer life．If we could keep the vitality and resistance to disease that we have at age twenty, we would live for 800 years．
【小題1】What does the underlined word “it” refer to?

A．Physical vitality．B．Stress．C．Aging．D．Physical resistance．
【小題2】Which of the following is not a change of aging?
A．People gradually lose their muscle strength．
B．Bones tend to break more easily．
C．The heart loses power and pumps less blood．
D．The lungs become unable to take in oxygen．
【小題3】The author believes the following except that     ．
A．human's life pattern is predictable
B．physical fitness can't stop the force of aging
C．human's lifetime will last longer than 75 years
D．a(chǎn)ll of the changes of aging take place deep inside the body
【小題4】How did Dr．Paul Seagle lengthen the lifetime of rats in his experiment?
A．By keeping their physical fitness．B．By cutting the calories in their diet．
C．By resetting their clock of aging．D．By limiting the protein in their diet．
【小題5】What is probably the best title for the article?
A．Two Great Experiments
B．The Mystery of Human Life
C．The Breakthrough in the Study of Aging
D．Ways to lengthen Human Life


【小題1】B
【小題2】D
【小題3】D
【小題4】D
【小題5】C

解析試題分析：
【小題1】B 推理題。根據(jù)本句we meet a stress，a stress that is greater than our physical resistance．Often，it is only a minor accident or chance infection(a disease caused by virus)，but this time，it brings life to an end．說明這里的it指上的stress，它讓我們的生命結(jié)束。
【小題2】D 細(xì)節(jié)題。根據(jù)文章第五段Most of the changes of aging take place deep inside the body．The lungs become less able to take in oxygen．Powerful muscles gradually lose their strength．The heart loses power and pumps less blood．Bones grow easier to break．說明ABC都是變老的變化，D項(xiàng)表述錯誤，肺部不是不能吸入氧氣，是吸入氧氣變少。
【小題3】D 推理題。根據(jù)文章第五段Most of the changes of aging take place deep inside the body．The lungs become less able to take in oxygen．Powerful muscles gradually lose their strength．The heart loses power and pumps less blood．Bones grow easier to break．這里很多變老的癥狀都表現(xiàn)在外在了，故D說法錯誤。
【小題4】D 細(xì)節(jié)題。根據(jù)文章倒數(shù)第四段a classic experiment nearly doubled the lifetime of rats，simply by cutting back the calories in their diet說明D正確。減少了飲食中的卡路里，與D項(xiàng)相符。
【小題5】C 主旨大意題。本文講述了一個新的科學(xué)發(fā)現(xiàn)，是對人類變老的研究，結(jié)果發(fā)現(xiàn)我們可以延長我們的衰老過程，以延長我們的生命。故C正確。
考點(diǎn)：考查科普類短文閱讀
點(diǎn)評：：本文講述了一個新的科學(xué)發(fā)現(xiàn)，是對人類變老的研究，結(jié)果發(fā)現(xiàn)我們可以延長我們的衰老過程，以延長我們的生命。科普類短文閱讀會遇見較多的生詞，在遇見生詞的時候要學(xué)會根據(jù)上下文語境進(jìn)行推理猜測其意思，減少語言的障礙，本文的關(guān)鍵在于細(xì)節(jié)的定位較為重要。

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