For many years, humans have tried to find the secret to staying young. Although it has yet to be discovered, we may be closer than ever to finding a way that can slow down the aging process. A recent study by researchers from Duke L Jniversity in the US found that cutting one sdaily intake of calories could slow down biological aging, which means you might be able to hang on to your youthful looks a little longer. Previous research has shown that calorie restrictions slow aging in worms, flies and mice. So researchers wondered if it could have the same effect on people.To find out, Daniel Belsky and her teamTo find out, Daniel Belsky and her team examined data from a study by the National Institute on Aging, based in the US, which involved 220 people. During the two-year study, 145 people in the restriction group cut their calorie intake by 25 percent. Meanwhile, 75 peoplein the control group maintained their normal diets.At the start of the study, the two groups had no difference inbiological age.The average participant was 38 years old, with a biological age of 37. However, after each 12- month period, participants in the restriction group saw an increase in biological age by an average of 0.1 1years. Meanwhile, those in the control group saw a rise by an average of 0.71 years. The researchers believe the difference between these groups shows that cutting calories does slow biological aging. Although they didn't explain the reason behind this, researchers at Brigham Young University in the US provided an explanation after they carried out a similar study on mice. Theybelieve fewer Calories slow down a mechanism in cells called the ribosome (核糖体)，at least in mice. The mechanism is responsible for making vital proteins in cells,but with fewer calories it slows down, giving it more time to repair itself, The ribosome is complex like a car, and itneeds to replace the parts that wearout the fastest from time to time, according to John Price, a biochemistry professor at Brigham Young University.“When tires wear out, you don't throw the whole car away and buy new ones. It's easier to replace the tires," Price told VOA. But this doesn't mean that people who want to look younger should start skipping meals, especially given the study's early stage. Proper nutrition is important, Price explained. “Food isn't just material to be burned -it's a signal that tells our body and cells how to respond,"he told Science Daily.The purpose of the research was ().A.test the influence of calorie restrictions on aging.B.explain why people have to maintain a normal diet.C.find the most efficient way to control calorie intake.D.invent technology that keeps people young and healthy.Which of the following statements is TRUE about the experiment ()?A.The biological age of people in the control group increased more than those in the restriction group.B.Some participants were asked to double the amount of food they ate.C.Flies and mice were used to compare the results of the human test with.D.AlI the participants were of the same biological age at the start.According to John Price, ().A.a higher level of calorie intake meansmore healthy proteins.B.reducing calorie intake could allow the ribosome to repair itself better.C.the fewer calories one takes in, the better the ribosome works.D.the ribosome is an important cell that controls the aging process.

第1题

完形填空Many of the world’s pollution problems have been caused by the crowding of lar

ge groups of people into cities.Satisfying the 21 of the people leads to further polluting by industry.If the rapid increase in human population 22 at the present rate (比率), there may be much greater harm.Some scientists speak of the 23 in number of people as “Population Pollution”.

About 2000 years ago, the world 24 was probably about 250 million.It reached a billion in 1850.By 1930 the population was two billion.It is 25 three and a half billion.It is expected to double by the year 2000.If the population continues to grow at the same 26 , there would be 25 billion people in the world a hundred years from now.

Man has been using the earth’s 27 more and more rapidly over the years.Some of them are almost gone.Now many people believe that man’s greatest 28 is how to control the growth of this population.The materials in the world will not support the human population in time to come if the present rate of increase continues.29 there is over crowding in the cities and hunger in some countries.Can man’s rate of increase continue？

Many people believe that human survival (幸存者) in the future 30 on the answer to the question.

21.A.needs

B.supplies

C.service

D.supports

22.A.stops

B.continues

C.slows down

D.adds to

23.A.increase

B.reduce

C.country

D.improvement

24.A.people

B.situation

C.population

D.land

25.A.now

B.in the past

C.in the future

D.then

26.A.place

B.time

C.rate

D.result

27.A coal

B.oil

C.mines

D.resources

28.A.problem

B.power

C.plan

D.idea

29.A.Already

B.Yet

C.Still

D.Often

30.A.feeds

B.lives

C.keeps

D.depends

点击查看答案

第2题

A computer is a machine designed to perform. work mathematically and to store and select i

nformation that has been fed into it. It is nm by either mechanical or electronic means. These machines can do a great deal of complicated work in a very short time. A large computer, for example, can add or subtract nine thousand times a second, multiply a thousand times a second, or divide five hundred times a second. Its percentage of error is about one in a billion digits. It has been estimated that human beings making calculations average about one mistake per two hundred digits.

The heart of an electronic computer lies in its vacuum tubes, or transistors. Its electronic circuits work a thousand times faster than the nerve cells in the human brain. A problem that might take a human being two years to solve can be solved by a computer in one minute, but in order to work properly, a computer must be given instructions--it must be programmed. Computers can be designed for many specialized purposes--they can be used to prepare payrolls, guide airplane flights, direct traffic, even to play chess. Computers play an essential role in modern automation in many plants and factories throughout the world.

A computer is a machine designed to ______.

A．perform. work mathematically

B．perform. complicated calculations

C．store and select information

D．all of the above

点击查看答案

第3题

听力原文：A computer is a machine designed to perform. work mathematically and to store and

听力原文： A computer is a machine designed to perform. work mathematically and to store and select information that has been fed into it. It is run by either mechanical or electronic means. These machines can do a great deal of complicated work in a very short time. A large computer, for example, can add or subtract nine thousand times a second, multiply a thousand times a second, or divide five hundred times a second. Its percentage of error is about one in a billion digits. It has been estimated that human beings making calculations average about one mistake per two hundred digits.

The heart of an electronic computer lies in its vacuum tubes, or transistors. Its electronic circuits work a thousand times faster than the nerve cells in the human brain. A problem that might take a human being two years to solve can be solved by a computer in one minute, but in order to work properly, a computer must be given instructions--it must be programmed.

Computers can be designed for many specialized purposes--they can be used to prepare payrolls, guide airplane flights, direct traffic, even to play chess. Computers play an essential role in modern automation in many plants and factories throughout the world.

(33)

A．One in a billion digits.

B．Zero.

C．One mistake per two hundred digits.

D．One in a million digits.

点击查看答案

第4题

Human beings have used tools for a very long time. In some parts of the world you can stil

l find tools that people used more than two million years ago. They made these tools by hitting one stone against another. In this way they broke off pieces from one of the stones. These chips of stone were usually sharp on one side. People used them for cutting meat and skin from dead animals, and also for making other tools out of wood. Human beings needed to use tools because they did not have sharp teeth like other meat eating animals, such as lions and tigers. Tools helped people to get food more easily.

Working with tools also helped to develop human intelligence. The human brain grew bigger, and human beings began to invent more and more tools and machines. The stone chip was one of the first tools that people used, and perhaps it is the most important. Some scientists say that it was the key to the success of mankind.

Since 1960 a new kind of tool has appeared. This is the silicon chip—a little chip of silicon crystal. It is smaller than a finger-nail, but it can store more than a million "bits" of information. It is an electronic brain.

Every year these chips get cleverer, but their size gets smaller, and their cost gets less. They are used in watches, calculators and intelligent machines that we can use in many ways.

In the future we will not need to work with tools in the old way. Machines will do everything for us. They will even talk and play games with us. People will have plenty of spare time. But what will they do with it？

Human beings used stone chips for more than two million years, but human life changed very little in that time. We have used silicon chips for only a few years, but life is changing faster every day. What will life be like twenty years from now？ What will the world be like two million years from now？

According to the passage, which of the following statements is NOT true？

A．Human beings used tools more than two million years ago.

B．Human beings used to have sharp teeth like other animals.

C．Human beings developed their intelligence by working with tools.

D．Human beings began to use stone chips a very long time ago.

点击查看答案

第5题

Many Native Americans closely resemble Asians. This has led most scientists to （1) believe somet

Many Native Americans closely resemble Asians. This has led most scientists to(1)believe something about Native Americans. They think that most Native Americans(2)from a distant group of people. These people(3)from Siberia across the Bering Strait, between 17,000-11,000 years ago. The exact time and 4 is still under question. That is, it is still a(n)(5)of debate. The time they traveled and the route they took is still being argued, as is whether it happened(6).

(7)recently, some anthropologists (人类学家) argued that the migration occurred 12,000 years ago. However, there are a number of difficulties with this theory —(8)particular, the presence of people in the Americas earlier than one might think. There is growing evidence of human(9)in Brazil and Chile 11,500 years ago or earlier. There is also(10)of humans living in the Americas some 50,000 years ago.(11), other possibilities have been suggested.

They may have(12)the land bridge several thousand years earlier or they may have sailed along the western coast. However, some(13)this theory. They think that humans(14)skills for sailing during that era.

Some consider the genetic and cultural evidence for an Asian origin overwhelming. It should be noted,(15), that some other people are very upset at this idea. Many present-day Native Americans(16)the above theories. They say those who put forward such theories have political(17)They have their own traditional stories that offer(18)of where they came from. Their own stories claim that their(19)are different from what scientists say. Those accounts, though, have mostly been(20)by scholars. Therefore, the origin of Americans still remains a mystery to be explored.

点击查看答案

第6题

Fifty years ago, most people lived in rural areas. But the world has changed. In the near

future, more than half of all people will live in cities for the first time in history.

City life is not always a bad thing, but many experts worry about this process of urbanization (城市化 ). A new report says that process is having a huge effect on human health and the quality of the environment. Of the three billion people who live in cities now, the report says, about one billion live in unplanned settlements. These are areas of poverty, slums that generally lack basic services like clean water, or even permanent housing. More than 60 million people are added to cities and surrounding areas each year, mostly in slums in developing countries. The international community has been too slow to recognize the growth of urban poverty. Policy makers need to increase investments in education, health care and other areas.

The report talks about some successful efforts by local governments and community groups. For example, it says in Columbia, engineers have created a bus system that has helped reduce air pollution and improve quality of life.

The link between urban poverty and the environment is serious, but governments also need to consider why people are moving out of rural areas. Climate changes, droughts, floods—there are many reasons forcing people to leave their farm land.

The two issues of poverty reduction and the environment have existed side by side, but rarely have they connected—until now. Governments are starting to understand that environmental collapse is not a natural cost of economic development. Instead, it is hurting the possibility for growth.

The main idea of the passage is about ______.

A．urbanization and its effects

B．a huge effect of human

C．economic development

D．the environment

点击查看答案

第7题

Passage Four:Questions 36 to 40 are based on the following passage:Time was—and not so man

y years ago, either—when the average citizen to ok a pretty dim view of banks and banking. That this was so, it should be said, was to no small extent the fault of banks and bankers themselves. Banks used to be—and a few still are—forbidding (令人生畏的) structures. Behind the little barred windows were, more often than not, elderly gentlemen w hose expression of friendliness reflected the size of the customer’s account, and nothing less than a few hundred thousand in the bank could have inspired the suggestion of a smile.

And yet the average bank for many years was, to the average citizen, a fearful, if necessary, instrument for dealing with business—usually big business. But somewhere in the 1930’s banks started to grow human, even pleasant, and started to attract the little man. It is possible that this movement beg an in medium-sized towns, or in small towns where people know each other by their first names, and spread to big towns. At any rate, the results have be en remarkable.

The movement to “humanize” banks, of course, received a new push during the war, when more and more women were employed to do work previously performed by men. Also more and more “little” people found themselves in need of personal loans, as taxes became heavier and as the practice of installment (分期付款) buying broke down the previously long-held concept that there was something almost morally wrong about being in debt. All sorts of people began to discover that the intelligent use of credit (信贷) could be extremely helpful

.

第36题：The author believes that the unfriendly atmosphere in banks many years a go was chiefly due to ________.

A) the attitude of bankers

B) unfriendliness of customers toward banks

C) economic pressure of the time

D) the outer appearance of bank buildings

点击查看答案

第8题

Botany, the study of plants, occupies a peculiar position in the history of human knowledg

e. For not many thousands of years it was the one field of awareness about which humans had anything more than the vaguest of insights(了解). It is impossible to know today just what our Stone Age ancestors knew about plants. But from what we can observe of pre-industrial societies that still exist, a detailed learning of plants and their properties must be extremely ancient. This is logical. Plants are the basis of the food pyramid for all living things, even for other plants. They have always been enormously important to the welfare of peoples, not only for food, but also for clothing, weapons, tools, dyes, medicines, shelter, and a great many other purposes. Tribes living today in the jungles of the Amazon recognize literally hundreds of plants and know many properties of each. To them botany, as such, has no name and is probab-ly not even recognized as a special branch of "knowledge" at all.

Unfortunately, the more industrialized we become, the farther away we move from direct contact with plants, and the less distinct our knowledge of botany grows. Yet everyone comes unconsciously on an amazing amount of botanical knowledge, and few people will fail to recognize a rose, an apple, or an orchid. When our Neolithic ancestors, living in the Middle East about 10,000 years age, discovered that certain grasses could be harvested and their seeds planted for richer yields the next season, the first great step in a new association of plants and humans was taken. Grains were discovered and from them flowed the marvel of agriculture: cultivated crops. From then on, humans would increasingly take their living from the controlled production of a few plants, rather than getting a little here and a little there from many varie-ties that grew wild and the accumulated knowledge of tens of thousands of years of experience and intimacy with plants in the wild would begin to fade away.

It is assumed in the passage that early humans ______.

A．probably had extensive knowledge of plants

B．thought there was no need to cultivate crops

C．did not enjoy the study of botany

D．placed great importance on the ownership of property

点击查看答案

第9题

A telescope, like a microscope, enables us to see things which we could not see without it

. A microscope magnifies things(or features of things)which are so small that they are invisible to the naked eye. They may be as small as a cell or even a small group of molecules. "Micro" in Greek, and in several English technical words, means "small". But "tele" in Greek means distant or far away. The word "television" is also derived from this Greek word. In England, Australia, and New Zealand we call a television set the "telly", which is almost the same as the Greek word. In the United States people call it a TV. A telescope enables us to see objects which, though millions of times larger than ourselves, appear much smaller because they are so far away. Even the images of stars which we see through a telescope are, of course, greatly reduced in size in comparison with the stars, actual size. But a telescope enables us to see stars which are invisible to the human eye as well as giving us a brighter, clearer image of those which are visible. In the last twenty or thirty years there has been a great improvement in the design and magnifying power of telescopes. There are now some very large and powerful telescopes in existence. When you see the sun rise in the morning you are eight minutes late. What is the meaning of this strange statement？ The fact is that it takes eight minutes for the light to travel from the sun to the earth. The speed of light is approximately 186,000 rails per second. When you see a planet with or without the help of a telescope you are again too late to see the planet as it exists when you look at it. You see it as it was some time earlier. What happens when you observe stars beyond the solar system？ Light from these stars takes a much longer time on its journey. In many cases it takes millions of years to reach our planet. Perhaps you believe that when you see a particular star, you and the star exist simultaneously. But this cannot be true. Be tween you and the star there are many millions of miles in space; and this means that there is also a long history of several million years between the star and you; in other words, the star which you are looking at now no longer exists in the form. in which you see it. Perhaps at this moment there is no star at that particular point in space. Stars, like human beings, are born and die.

A microscope______.

A．may be as small as a cell or a small group of molecules

B．is similar to a telescope

C．enables us to see things that are invisible

D．enables us to see things that are too small to be seen

点击查看答案

第10题

Mountain climbers around the world dream about going up Mountain Everest （珠穆朗玛峰) . It

Mountain climbers around the world dream about going up Mountain Everest (珠穆朗玛峰) . It is the highest mountain in the world. But many people who have climbed the mountain have left waste material that is harming the environment.

A team of Americans is planning the largest clean-up effort ever on Mountain Everest. They will make the risky trip up the mountain next month.

The team of eight Americans will be guided by more than twenty Sherpas of Nepal (尼泊尔夏尔巴人).Their goal is to remove all the trash they see. They will spend two months cleaning up the mountain by gathering oxygen bottles, fuel containers, batteries, drink cans, human waste and other kinds of trash. They are expected to remove at least three tons of trash in large bags.

Team leader Robert Hoffman is making his fourth trip up the mountain. He says he hopes to bring Everest to the condition it was in before the first successful climb fifty years ago. He says he hopes the effort will influence other people to clean up the environment closer home.

Human waste on Everest is a major concern. So the clean-up team will take along newly development equipment to collect and treat human waste. Over the years, the waste articles have polluted the mountain. In the warm season when the ice melts, the polluted water flows to Nepali villages below. The problem has gotten worse in recent years because climbing Everest has become more popular.

When those Americans are planning the trip up Mountain Everest, they are concerned about______.

A．the success in climbing up the mountain

B．the environment pollution of the mountain

C．the equipment for their trip to the mountain

D．the risks facing the mountain climbers

点击查看答案

第11题

Who designed the first helicopter? Who(1)one of the most famous pictures in th

e world? Who knew more about the human body than most(2)? There is an answer

(3)all these questions - Leonardo de Vinci (达芬奇),Leonardo may have been the greatest genius(4)have ever known. He lived in Italy around the year 1500, but many of his inventions seem modern to us today. For example, one of his notebooks has drawings of a helicopter. Of course, he couldn' t(5)a helicopter with the things he had. But scientists say his idea would have worked. But Leonardo(6)an inventor. He was one of the greatest a rtists of his day. By the time he was twenty years old, he was called a master painter, and as he got older he became(7)more famous. Sometimes he drew a hand ten different ways(8)he was ready to paint.Many of Leonardo' s wonderful paintings are still with(9) today. You may know one of his most famous works the(10)woman known as theMona Lisa.

1.A. took

B.made

C.painted

D.invented

2.A.artists

B.doctors

C.painters

D.people

3.A.to

B.of

C.for

D.from

4.A.the scientists

B.the artists

C.the world

D.people

5.A.draw

B.paint

C.work

D.build

6.A.was just

B.wasn't just

C.wasn't

D.was no longe

7.A.less

B.no

C.even

D.very

8.A.before

B.after

C.because

D.when

9.A.him

B.us

C.them

D.you

10.A.interesting

B.crying

C.smiling

D.surprising

点击查看答案