If you can find a tree which has been cut down，you will see many rings，or circles，on the base of the trunk.By learning to read these rings，you can find out about the tree's life.

    The number of rings tells you how old the tree is.Each year，new wood is formed on the outside of the tree.This new wood is light in color when the tree is growing in spring and summer，and dark in winter when the tree is not growing much.So，if you count the rings of dark­or­light colored wood，you can often find out how old the tree is.

    You can also tell which years have been good years and which years have been bad years.When the light­colored rings are very wide，it means that the tree has been growing quickly that year.If the rings are narrow，it has been growing slowly.If the rings on a tree trunk were greatly magnified，you would be able to see why the rings are light­colored when the tree is growing quickly and dark­colored when the tree is growing slowly.The tree trunk is made up of microscopic tubes，like some pipes，carrying water from the soil，through the trunk，and up to the leaves.They are wide and thin­walled when the tree is growing quickly and they are carrying a lot of water.They are narrow and stuck together when the tree is not growing so quickly.

    When a tree is old，the tubes in the centre of the tree don't carry water.The walls of the tubes have become thick with materials which have stuck along them over the years，forming a kind of wood called“heartwood”．This kind of wood is darker in color than the young，growing wood on the outside of the tree.

    You don't very often see whole tree trunks which have been cut across.But once you learn to read a cross section of the wood，you can see much more in wood which has been used to make boxes，houses and other things.

    In most wood，instead of seeing the trunk cut across，you are seeing it cut along its length.Because you don't see the whole tree，you can't tell how old it is.

Title：{#blank#}1{#/blank#} of a Tree

    When it comes to the Internet, passwords which people often use are under fire. {#blank#}1{#/blank#} Research has shown that passwords are not a very good way to protect sensitive information.

    People would use some random characters, numbers and symbols. Furthermore, a unique password would be used for every site or application the user uses. Unfortunately, the more complex they become, the more people are likely to forget their passwords. The longer the passwords are, the more easily forgotten they are.{#blank#}2{#/blank#} 

    Google is trying to kill off the password on Android devices by introducing the Trust API, which does what simple passwords cannot. It gives developers a framework for securing their applications using a number of security systems and metrics (指标)on the device. A Trust Score will be generated based on the metrics the device gathers. {#blank#}3{#/blank#} 

    The Trust Score will be generated based on both metrics like your device location, face scanning, fingerprint and so on. Taken one at a time, these metrics arc not secure. But taken together, these metrics will help define the real "you".

    {#blank#}4{#/blank#}  This summer, Google will be running tests with some banks to see if Trust API meets their needs before rolling out to all developers later this year. It may take another year for apps and popular sites to start using the Trust API.

    This is a pretty exciting change. Passwords have been around for long and although the security of systems has been improved, the convenience of systems hasn't been improved much. {#blank#}5{#/blank#}  Maybe that never-ending conflict between security and convenience will be able to take a break once the Trust system comes out.

A. Google appears to have the best of them.

B. Actually it's been under fire for a long time.

C. People tend to care more about its advantages.

D. Google has already been testing this on the real world.

E. Google has proved that the system is more convenient.

F. Therefore, they use the same password for each application.

G. It'll allow or refuse your application based on your trust score.

    If humans were truly at home under the light of the moon and stars，we would go in darkness happily，the midnight world as visible to us as it is to the vast number of nocturnal(夜间活动的) species on this planet. Instead，we are diurnal creatures, with eyes adapted to living in the sun's light. This is a basic evolutionary fact, even though most of us don't think of ourselves as diurnal beings. Yet it's the only way to explain what we've done to the night: We've engineered it to  receive us by filling it with light.

    The benefits of this kind of engineering come with consequences 一 called light pollution 一 whose effects scientists are only now beginning to study. Light pollution is largely the result of bad  lighting design，which allows artificial light to shine outward and upward into the sky. III-designed lighting washes out the darkness of night and completely changes the light levels 一 and light  rhythms — to which many forms of life, including, ourselves, have adapted. Wherever human light spills into the natural world, some aspect or life is affected .

    In most cities the sky looks as though it has been emptied of stars, leaving behind a vacant haze(霾) that mirrors our fear of the dark. We've grown so used to this orange haze that the original glory of an unlit nigh, - dark enough for the planet Venus to throw shadow on Earth, is wholly beyond our experience, beyond memory almost.

    We^'ve lit up the night as if it were an unoccupied country, when nothing could be further form the truth. Among mammals alone, the number of nocturnal species is astonishing, Light is a powerful biological force, and on many species it acts as a magnet(磁铁). The effect is so powerful that scientists speak of songbirds and seabirds being “captured” by searchlights on land or by the light from gas flares on marine oil platforms. Migrating at night, birds tend to collide with brightly lit tall buildings.

    Frogs living near brightly lit highways suffer nocturnal light levels that are as much as a million times righter than normal, throwing nearly every aspect of their behavior out of joint including most other creatures ,we do need darkness .Darkness is as essential to our biological welfare, to our internal clockwork, as light itself.

    Living in a glare of our making,we have cut ourselves off from our evolutionary and cultural heritage—the light of the stars and the rhythms of day and night .In a very real sense light pollution causes us to lose sight of our true place in the universe, to forget the scale of our being, which is best measured against the dimensions of a deep night with the Milky Way—the edge of our galaxy arching overhead.

    Teenagers who talk on the phone a lot and hold their cell phones up to their right ears score worse on one type of memory test. That's the finding of a new study. That memory damage might be one side-effect of the radiation that phones use to keep us connected while we're on the go.

    Nearly 700 Swiss teens took part in a test of figural memory. This type helps us recall abstract symbols and shapes, explains Milena Foerster. She's an epidemiologist(流行病学家). She worked on the study as part of a team while Foerster was at the Swiss Tropical and Public Health Institute in Basel, Switzerland. Teens participated memory tests twjce, one year apart. Each time, they had one minute to memorize 13 pairs of abstract shapes. Then they were shown one item from each pair and asked to match it with one of five choices.

    The study volunteers also took a test of verbal memory. That's the ability to remember words. The two memory tests are parts of an intelligence test.

    The researchers also surveyed the teens on how they use mobile phones. And they got call records from phone companies. The researchers used those records to estimate how long the teens were using their phones. This allowed the researchers to calculate how big a radiation exposure each person could have gotten while talking.

    All cell phones give off energy in the form of radio frequency electromagnetic fields, or RF-EMFs. Radio and TV broadcasts also use this type of energy. So do microwave ovens and some other gadgets(配件).

    "For a phone, that energy carries information, in the form of calls or texts between phones and cell phone towers. That radiation also can travel into people's bodies as they use their phones. And some of its energy can be absorbed by the body. So far, scientists have not shown that radiation from phones causes harm," says the Federal

    Communications Commission. Research is ongoing, this agency notes.

    You've probably heard such reports. The number of college students majoring in the humanities (人文学科) is decreasing quickly. The news has caused a flood of high-minded essays criticizing the development as a symbol of American decline.

    The bright side is this: The destruction of the humanities is, finally, coming to an end. No more will literature, as part of an academic curriculum, put out the light of literature. No longer will the reading of, say, "King Lear" or D.H. Lawrence's "Women in Love" result in the annoying stuff of multiple-choice quizzes, exam essays and homework assignments.

    The discouraging fact is that for every college professor who made Shakespeare or Lawrence come alive for the lucky few, there were countless others who made the reading of literary masterpieces seem like two hours in the dentist's chair.

    The remarkably insignificant fact that, a half-century ago, 14% of the undergraduate population majored in the humanities (mostly in literature, but also in art, philosophy, history, classics and religion) as opposed to 7% today has given rise to serious reflections on the nature and purpose of an education in the liberal arts.

    Such reflections always come to the same conclusion: We are told that the lack of a formal education, mostly in literature, leads to numerous harmful personal conditions, such as the inability to think critically, to write clearly, to be curious about other people and places, to engage with great literature after graduation, to recognize truth, beauty and goodness.

    Literature changed my life long before I began to study it in college. Books took me far from myself into experiences that had nothing to do with my life, yet spoke to my life. But once in the college classroom, this precious, alternate life inside me got thrown back into that dimension of my existence that bored me. Homer, Chekhov and Yeats were reduced to right and wrong answers, clear-cut themes and clever interpretations. If there is anything to worry about, it should be the disappearance of what used to be an important part of every high-school education: the literature survey course, where books were not academically taught but thoroughly introduced—an experience unaffected by stupid commentary and useless testing.

    The literary classics are places of quiet, useless stillness in a world that despises (鄙视) any activity that is not profitable or productive. Literature is too sacred to be taught. It needs only to be read.

    Soon, if all goes well and literature at last disappears from the undergraduate curriculum—my fingers are crossed—increasing numbers of people will be able to say that reading the literary masterworks of the past outside the college classroom, simply in the course of living, was, in fact, their college classroom.

I am asked repeatedly why anyone would want to keep an "'ugly" building or a building that is dirty and clearly in need of work, I guess you could say we preservationists (文物保护者)look at buildings through a different angle - an angle that can see the swan in the ugly duck the story in the simple lines, and the book behind the cover.

The Queen Emma Building is remembered by many as one of the ugliest buildings in town. Yet the angle from which a preservationist views the building is that it is uniquely constructed with an artistical sun shield to block the sunlight, a decorative wall designers used concrete bricks to form. Unfortunately, it was removed in 20il, making the building one of many contemporary buildings in town.

Other times, when a beautiful site is replaced by a "horrible" building, people hate it and can't get over their anger, even when that: "horrible" building becomes an important part of our story. This is particularly true in San Francisco with many Victorian buildings, which are many preservationists' favorite. Yes, it was a tragedy, that many Victorian buildings got torn down several decades ago, but those losses also tell another important story. It tells the story of the1950s and 1960s when there was hope for a more equal society with in expensive housing for the working class. Should that history be wiped from our memories? 

Preservation is not just about keeping pretty, well-kept buildings, but about holding on to parts of our history - not just the history of huge events, but the story of how everyone used to go to a certain corner market. Our history cannot be told only in buildings that meet someone's criteria of beauty, sometimes our history is, painful, but no less important.