单选题
Why we age is the subject of vigorous debate. The classical view is that aging happens because of random wear and tear. A newer view holds that aging is more orderly and genetically driven. Proponents of this view point out that animals of similar species and exposure to wear and tear have markedly different life span. The Canada goose has a longevity of 23. 5 years; the emperor goose only 6. 3 years. Perhaps animals are like plants, with lives that are to a large extent, internally governed. Certain species of bamboo, for instance, form a dense stand that grows and flourishes for a hundred years, flowers all at once, and then dies. The idea that living things shut down and not just wear down has received substantial support in the past decade. Researchers working with the now famous worm C. elegans(two of the last five Nobel Prizes in medicine went to scientists doing work on the little nematode)were able to produce worms that live more than twice as long and age more slowly by altering a single gene. Scientists have since come up with single-gene alterations that increase the life spans of Drosophila fruit flies, mice and yeast. These findings notwithstanding, scientists do not believe that our life spans are actually programmed into us. After all, for most of our hundred-thousand-year existence—all but the past couple of hundred years—the average life span of human beings has been thirty years or less.(Research suggests that subjects of the Roman Empire had an average life expectancy of twenty-eighty years.)Today the average life span in developed countries is almost eighty years. If human life spans depend on our genetics, then medicine has got the upper hand. We are, in a way, freaks living well beyond our appointed time. So when we study aging, what we are trying to understand is not so much in a natural process as an unnatural one. Inheritance has surprisingly little influence on longevity. James Vaupel, of the Max Planck Institute for Demographic Research, in Rostock, Germany, noted that only six percent of how long you"ll live, compared with the average, is explained by your parents" longevity; by contrast, up to ninety percent of how tall you are, compared with the average, is explained by your parents" height. Even genetically identical twins vary widely in life span: the typical gap is more than fifteen years.
单选题
The example of goose"s life span shows that______.
【正确答案】
D
【答案解析】解析：由题干中的“goose”定位至首段。第四句指出“Proponents of this view point out that animals of similarspecies and exposure to wear and tear have markedly different life span．”而Canada goose和emperor goose寿命不同正是对该句的例证说明。选项D与“animals of similar species and exposure to wear and tear havemarkedly different life span”意思相同，故为答案。
单选题
What, as the author mentions in this article, is genetically determined?
【正确答案】
A
【答案解析】解析：由题干中的“genetically”定位至第二段。该段提到了gene，末句指出“Scientists have since come upwith single-gene alterations that increase the life spans of Drosophila fruit flies，mice and yeast．”显然，这里提到的是基因和life span之间的关系，life expectancy与life span都意为“寿命”，故A为答案。
单选题
It can be assumed that people in the past several hundreds of years______.
【正确答案】
A
【答案解析】解析：由题干中的“hundreds of years”定位至第三段第二句“…the past couple of hundred years—the averagelife span of human beings has been thirty years or less”。选项A是对该部分内容的同义转述，故为答案。
单选题
While twins have many things in common, only one feature is mentioned in this article. What is it?
【正确答案】
C
【答案解析】解析：由题干中的“twins”定位至末段最后一句“Even genetically identical twins vary widely in life span：thetypical gap is more than fifteen years．”显然文章提到的只是双胞胎的寿命问题，不涉及其他方面，故C为答案。