Nowadays people are facing lots of threats（威胁）all over the world.

   A serious threat to farmers in many parts of the world is erosion（侵蚀）.Erosion happens if a large area of land is cleared of trees and is then badly treated by the farmers.The rain and winds may gradually wash away,or blow away much of the topsoil.When this happens,crops of wheat and corn become weaker and weaker until nothing grows well.If erosion continues,it will turn good land into a desert.

    In the past,when erosion appeared,farmers sometimes moved to a new place to farm.Sometimes they could not move,but continued to try to grow food in the unhealthy soil.This caused them to sink into poverty.Soon some people realized that there was little rich,fertile soil in the world.The government began to try to stop erosion.

    One of the first experiments to stop erosion began in the United States in 1933.The experiment was carried out in the area of the Tennessee River.Flood and bad farming in this area had ruined the land that had once been rich.As a result,most of the people living around the Tennessee River were very poor.

The government built big dams across the river and stored the water for use during the dry season,when there was no rain.The government workers also helped the farmers fertilize their soil and to learn new farming methods which could stop erosion.

    In the beginning,the farmers were not interested.But soon,good healthy crops began to appear on the land where new methods were used.Ten years after that the crops were extremely good.The great success of this experiment led to similar projects in other parts of the world.

With the development of science and technology,people are trying to get rid of all the threats they are facing. However,it's not an easy job,because at the same time people are polluting their homeland.

    Grey clouds move as low as smoke over the treetops at Lolo Pass. The ground is white. The day is June 10.It has been snowing for the past four days in the Bitterroot Mountains.Wayne Fairchild is getting worried about our trek over the Lolo Trail-95 miles from Lolo Montana to Weippe in Idaho, across the roughest country in the West. Lewis and Clark were nearly defeated 200 years ago by snowstorms on the Lolo. Today Fairchild is nervously checking the weather reports. He has agreed to take me across the toughest, middle section of the trail.

    When Lewis climbed on top of Lemhi Pass,140 miles south of Missoula, on Aug.12,1805,he was astonished by what was in front of him; "high mountain chains still to the West of us with their tops partially covered with snow.＂Nobody in what was then the US knew the Rocky Mountains existed, with peaks twice as high as anything in the Appalachians back East.

    Today their pathway through those mountains holds more attraction than any other ground over which they traveled, for its raw wilderness is an evidence to the character of two cultures:the explorers who braved its hardships and the Native Americans who prize and conserve the path as a sacred (神圣的)gift. It remains today the same condition as when Lewis and Clark walked it.

    The Lolo is passable only from July to mid-September. Our luck is holding with the weather, although the snow keeps getting deeper. As we climb to Indian Post Office, the highest point on the trail at 7,033 ft, we have covered 13 miles in soft snow, and we hardly have enough energy to make dinner. After a meal of chicken, I sit on a rock on top of the ridge .There is no light visible in any direction, not even another campfire. For four days we do not see another human being. We are occupied with the things that mix fear with joy. In our imagination we have finally caught up with Lewis and Clark.

    The National Gallery

    Description:

    The National Gallery is the British national art museum built on the north side of Trafalgar in London. It houses a diverse collection of more than 2,300 examples of European art ranging from 13th-century religious paintings to more modern ones by Renoir and Van Gogh. The older collections of the gallery are reached through the main entrance while the more modern works in the East Wing are most easily reached from Trafalgar Square by a ground floor entrance.

    Layout:

    The modern Sainsbury Wing on the western side of the building houses 13th-to15th-century paintings, and artists include Duccio, Uccello, Van Eyck, Lippi, Mantegna, Botticelli and Memling.

    The main West Wing houses 16th-century paintings and artists include Leonardo da Vinci, Cranach, Michelangelo, Raphael, Bruegel, Bronzino, Titian and Veronese.

    The North Wing houses 17th-century paintings and artists include Caravaggio, Rubens, Poussin, Van Dyck, Velazquez, Claude and Vermeer.

    The East Wing houses 18th-to early 20th-century paintings, and artists include Canaletto, Goya, Turner, Constable, Renoir and Van Gogh.

    Opening Hours:

    The Gallery is open every day from 10am to 6pm（Fridays 10am to 9pm）and is free, but charges apply to some special exhibitions.

    Getting There:

    Nearest underground stations: Charing Cross (2-minute walk). Leicester Square (3-minute walk), Embankment (7-minute walk), and Piccadilly Circus (8-minute walk).

    My friend Jason and I wanted to do something to help other people who are less lucky and help us grow at the same time. After we decided that we would volunteer in Nepal, I did some surveys on the Internet and I found an organization called Volunteer(志愿者) Nepal and felt strongly that it was the right choice for us.

    While making our plans, Jason and I realized that others might like the chance to be a part of our experience. So before leaving for Nepal, we asked the people we know whether they would be interested in donating(捐赠) money or goods to Nepal Orphans Home.

    One friend, whose family owns a shop called Drake Supermarket, told others about it. Many people wanted to donate something. We received donations that filled 29 boxes with sporting goods, toys, coloring books, pencils, children's books, and more, The boxes were later taken to Drake's warehouse(仓库) where I prepared them for shipment. Drake agreed to ship them to Nepal for free .

    The boxes had arrived at the Volunteer House when we arrived there. The next day, Jason and I opened the boxes. The children from the orphanages(孤儿院) stood in a line and were able to choose a gift. This took about an hour, but the looks on their faces and the happiness that we saw in their eyes made it one of the best days of our life.

    We visited the orphanages there in the following days. Being with the children at the orphanages was both sad and wonderful. I'm sure that anyone who has volunteered will understand what I mean by that. My experience as a volunteer was very useful. It has changed me as a person and the way I viewed life in the past.

    Teachers say the digital age has had a good influence and a not-so-good influence on this generation of American teenagers. More than 2,000 middle and high school teachers took an online survey. Researchers also spoke with teachers in focus groups.

    Three-quarters of the teachers said the Internet and digital search tools have had a "mostly positive" effect on their students' research habits and skills. But 87 percent agreed that these technologies are creating an "easily distracted generation with short attention spans (持续时间)". And 64 percent said the technologies "do more to distract students than to help them academically(学业上)". Many students think "doing research" now means just doing a quick search on Google.

    The Pew Internet Project did the survey with the College Board and the. National Writing Project. Most of the teachers came from Advanced Placement classes, which provide college-level work for high school students.

    Judy Buchanan is director of the National Writing Project and a co-author of the report. Ms. Buchanan says digital research tools are helping students learn more, and learn faster. Teachers really welcome these tools because they are ways to make some of learning exciting and engaging. Young people welcome these tools. And the goal is to really help them become creators of content, and meaningful content, and not just sort of consumers.

    But one problem the survey found is that many students are lacking in digital literacy. In other words, they trust too much of the information they find on the Internet. Another problem the survey found is blamed on something that might not seem like a problem at all: being able to quickly find information online.

    Teachers say the result is a reduction in the desire and ability of their students to work hard to find answers. They say students are depending too much on search engines and do not make enough use of printed books or libraries. Many teachers are also concerned that the Internet makes it easy for students to copy work done by others instead of using their own abilities.

Muir Woods and Sausalito Half Day Tour

    Wander through an ancient coastal redwood forest and explore the artistic bayside on this half-day tour from San Francisco. Travel across the Golden Gate Bridge to visit Muir Woods, home to some of the oldest and tallest trees on Earth. At the end of your tour choose between getting dropped off at Union Square in San Francisco or taking the ferry back to San Francisco.

    Yosemite National Park and Giant Sequoias Day Trip

    Discover the beauty of the Sierra Nevada on this full-day trip to Yosemite National Park from San Francisco. Travel aboard a comfortable van through historic Gold Rush towns to reach the park, where you'll be amazed by supersized natural wonders. Take a hike among ancient trees, and enjoy several hours to explore the park's wonders on your own.

    Niagara Falls Tour

    Escape from New York City and head north to see both sides of the Canadian border on this guided, 2-day tour to Niagara Falls. Visit Niagara Falls on both the American and Canadian sides and take a ride on the famous Maid of the Mist boat. Then, on the road back to New York City, make a stop to shop at the Crossings Premium Outlets, one of the largest outlet malls in the US.

    Napa and Sonoma Wine Country Tour

    Escape to California's famous wine country on this full-day tour from San Francisco. Taste regional varietals at three different wineries including both big-name and family-run estates (庄园). Learn about the winemaking process during guided tours, and appreciate the regional culture with a stop for lunch.