1.C 短文第一段的大致意思是，许多疾病都由病毒引起，诸如水痘、感冒和艾滋病，所以人们想尽办法躲避病毒。这是C所表达的意思。A不是正确选择，因为文章并没有说人们想方设法去杀死病毒。B的后半句的内容(病毒肉眼看不见)和D的内容(吃药治疗病毒引起的疾病)文中没有提到。 2.C短文的第二段明确提供了答案。
3.D 根据上下文，shrink在此的意思是“收缩\，即“缩小\。所以，它的反义词是expand(增大，扩张)。C不是正确选择，因为extend的意思是become longer，即“延伸”或“加长\。A的意思是“加宽”，也不是答案。B的意思是“伸展，展开\，在一定的上下文里也可以做shrink的反义词，但在第五段这个语境里，B不是最佳选择。
4.D 第六段第二句中提到的metallic disk是指“金属圆盘”，它是微型电池的外形，其内部是由病毒构成的电池部件。微型电池不是由金属组成的，所以A不是答案。本段提到，这种电池looks like a regular watch battery，与手表里电池外形相似，但并不等同手表电池，所以B也不是正确选择。文章只是说电池的部件(但并没有说整个电池)小到只能用显微镜才能看到，所以C也不是正确的选择。D才是第六段所要表达的主要内容，因此是答案。
5.A 短文最后一段的第四句(“you could probably fit about 10 of these virus-built battery parts，side to side，across one hair”)提供了本题的答案
第三十八篇
Longer Lives for Wild Elephants
Most people think of zoos as safe places for animals，where struggles such as difficulty finding food and avoiding predators don’t exist. Without such problems，animals in zoos should live to a ripe old age1. But that may not be true for2 the largest land animals on Earth. Scientists have known that elephants in zoos often suffer from poor health. They develop diseases，joint problems and behavior changes. Sometimes, they even become infertile，or unable to have babies.
To learn more about how captivity affects elephants，a team of international scientists compared the life spans of female elephants born in zoos with female elephants living outdoors in their native lands. Zoos keep detailed records of all the animals in their care，documenting factors such as birth dates, illnesses, weight and death. These records made it possible for me researchers to analyze 40 years of data on 800 African and Asian elephants in zoos across Europe. The scientists compared the life spans of the zoo-born elephants with the life spans of thousands of
female wild elephants in Africa and Asian elephants that work in logging camps3，over approximately the same time period.
The team found that female African elephants born in zoos lived an average of 16.9 years. Their wild counterparts who died of natural causes lived an average of 56 years-more than three times as long. Female Asian elephants followed a similar pattern. In zoos，they lived 18.9 years，while those in the logging camps lived41.7 years.
Scientists don't yet know why wild elephants seem to fare so much better than their zoo-raised counterparts. Georgia Mason，a biologist at the University of Guelph in Canada who led the study，thinks stress and obesity may be to blame4.Zoo elephants don't get the same kind of exercise they would in the wild，and most are very fat. Elephant social lives are also much different in zoos than in the wild，where they live in large herds and family groups.
Another finding from the study showed that Asian elephants born in zoos were more likely to die early than Asian elephants captured in the wild and brought to zoos. Mason suggests stress in the mothers in zoos might cause them to have babies that are less likely to survive. The study raises some questions about acquiring more elephants to keep in zoos. While some threatened and endangered species living in zoos reproduce successfully and maintain healthy populations，that doesn't appear to be the case with elephants. \，zoos are net consumers of elephants，not net producers,\ 词汇：
predator n.食肉动物 captivity/ n.监禁;束缚 ripe adj.成熟的 fare v.过活，生活
infertile adj.不生育的 obesity n.过度肥胖;肥胖症 注释：
1.1ive to a ripe old age：这是一种固定用法，意思是live to an age that is considered to be very old(长寿，高寿)。
2.be true for：或者be true of：对??适用。短文中第二段第一句：But that may not be true for
the largest land animals on Earth.这里，作为主语的that指的是第一段所陈述的内容。这个句子要传达的意思是：动物园对其他动物来说是一个安栖之地，而对大象来说却不然。
3.logging camps：伐木场。Logging作为名词，意思是：伐木业。 4.stress and obesity may be to blame：压力和肥胖是问题的根源。be to blame：该受责备，应承担责任。 练习：
1.According to the first two paragraphs，unlike other zoo animals，zoo elephants
A.have difficulty eating food. B.1ive to a ripe old age. C.are not afraid of predators. D.develop health problems.
2.Which of the following about the international scientists' research on the life spans of elephants is NOT true?(See paragraph 3)? A.They compared zoo elephants with wild elephants.
B.They kept detailed records of all the elephants in their care. C.They analyzed the records of the elephants kept in zoos. D.The zoo-born elephants they studied are kept in European zoos. 3.What do the scientist find in their research? A.Female elephants live longer than male elephants.
B.Female zoo elephants live longer than their wild counterparts. C.Female zoo elephants die much earlier than their wild counterparts. D.Elephants in zoos and those in the wild enjoy the same long life spans.
4.What are the possible causes of stress and obesity Zoo-raised elephants generally suffer from?
A.They do not like living in herds. B.They do not get enough exercise. C.They do not live with their families. D.Both B and C.
5.Which of the following does the author suggest in the last paragraph 7?
A.It may not be a wise policy to keep elephants in the zoo. B. Elephants are no longer an endangered species.
C.Zoo-born elephants should be looked after more carefully. D.Zoos should keep more animals except elephants. 答案与题解：
1.D 短文的第一段告诉我们，人们通常认为动物园内的动物没有猎食的困难，也不受其他猎食动物的威胁，所以一般寿命较长。但第一段并没有提及大象。第二段则说，动物园内的大象却不然，它们面临很多健康问题。所以，除了D以外，其他选项均不符合这两段内容。
2.B 第三段告诉我们，动物园，而不是这些研究人员，保存了所有园内动物的详细相关信息。所以应该选择B。其他三个选项均能在该段中找到相关内容。 3.C 短文的第四段提供了答案。该段告诉我们，野生的雌性大象的平均寿命是动物园里的雌性大象平均寿命的3倍还多。
4.D 短文的第五段提供了答案。该段第三句的意思是：动物园里的大象不像野生大象那样活动，因此非常肥胖。他们也不像野生大象那样过着群居的生活，即live in herds and family groups。
5.A 短文通篇陈述了大象在动物园内的生存问题，最后一段是全文的总结。该段第一句指出，对动物园大象的研究向人们提出了一个问题：是否应该将更多的大象关进动物园。该段还重复了第一、第二段的观点：其他动物在动物园能够很好地繁衍生息，而大象却不能。所以，A是正确选择。B、C、D均没有在文中被提及
第四十五篇
Some People Do Not Taste Salt Like Others
Low-salt foods may be harder for some people to like than others，according to a study by a Penn State College of Agricultural Sciences1 food scientist. The research indicates that genetic factors influence some of the difference in the levels of salt we like to eat.
Those conclusions are important because recent，well-publicized efforts to reduce the salt content in food2 have left many people
struggling to accept fare that simply does not taste as good to them as it does to others3，pointed out John Hayes，assistant professor of food science，who was lead investigator4 on the study.
Diets high in salt can increase the risk of high blood pressure and stroke. That is why public health experts and food companies are working together on ways to help consumers lower salt intake through foods that are enjoyable to eat. This study increases understanding of salt preference and consumption.
The research involved 87 carefully screened participants who sampled salty foods such as soup and chips，on multiple occasions，spread out over weeks5.Test subjects were 45 men and 42 women，reportedly healthy，ranging in age from 20 to 40 years. The sample was composed of individuals who were not actively modifying their dietary intake and did not smoke cigarettes. They rated the intensity of taste on a commonly used
scientific scale，ranging from barely detectable to strongest sensation of any kind.
“Most of US like the taste of salt. However，some individuals eat more salt，both because they like the taste of saltiness more，and also because it is needed to block other unpleasant tastes in food. \Hayes.\Supertasters，people who experience tastes more intensely，consume more salt than nontasters do. Snack foods have saltiness as their primary flavor，and at least for these foods，more is better，so the supertasters seem to like them more.”
However，supertasters also need higher levels of salt to block unpleasant bitter tastes in foods such as cheese，Hayes noted. \example，cheese is a wonderful blend of dairy flavors from fermented milk，but also bitter tastes from ripening that are blocked by salt,\he said. \is too pronouncedo6.\
Hayes cited research done more than 75 years ago by a chemist named Fox and a geneticist named Blakeslee，showing that individuals differ in their ability to taste certain chemicals. As a result，Hayes explained，