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．

1.What does the underlined word “it” refer to?

A．Physical vitality．   B．Stress．           C．Aging．           D．Physical resistance．

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．zxxk

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

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．

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

 

【答案】

1.B

2.D

3.D

4.D

5.C

【解析】

試題分析：本文主要介紹了人類變老的過程以及科學(xué)家在研究變老的過程中取得的突破性成就。

1.B 推理題。根據(jù)本句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說明這里的it就是指本段的stress，正是這樣的壓力讓我們的生命到了盡頭，故B正確。

2.D 細(xì)節(jié)題。根據(jù)第4段．The lungs become less able to take in oxygen說明我們的肺不是不能吸吸入氧氣，而是吸入的氧氣較少。故D項(xiàng)說法錯(cuò)誤。這不是變老的變化。

3.D 推理題。根據(jù)文章2,3,4,5段內(nèi)容可知這些變老的癥狀都是在人的內(nèi)部演變發(fā)生的，故D項(xiàng)的描述正確。故D正確。

4.D 細(xì)節(jié)題。根據(jù)文章倒數(shù)第3段2,3行The result was achieved through a special protein limited \diet，which had a great effect on the chemistry of the brain．說明D正確。

5.C 主旨大意題。本文在前部部分講述的是人的變老的過程，在最后幾段都是說明的是人類在研究變老的過程中取得的突破，故C項(xiàng)正確。

考點(diǎn)：考查科普類短文閱讀

點(diǎn)評(píng)：本文屬于科普類短文，此類文章的最大的障礙是詞匯以及考生對(duì)閱讀內(nèi)容的不熟悉，需要考生在閱讀的時(shí)候有足夠的耐心。要養(yǎng)成在上下文串聯(lián)中猜測(cè)詞義的能力，根據(jù)上下文中出現(xiàn)的同義詞，近義詞，反義詞，以及詞義的解釋來理解生詞。同時(shí)要抓住文章的中心，不要受其他信息的影響。要根據(jù)題目及選項(xiàng)以及文章的上下文串聯(lián)合理的判斷推理。

 

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