Disposing(处理) of waste has been a problem since humans started producing it. As more and more people choose to live close together in cities, the waste-disposal problem becomes increasingly difficult.

    During the eighteenth century, it was usual for several neighboring towns to get together to select a faraway spot as a dumpsite. Residents or trash haulers(垃圾托运者) would transport household rubbish, rotted wood, and old possessions to the site. Periodically(定期的) some of the trash was burned and the rest was buried. The unpleasant sights and smells caused no problem because nobody lived close by.

    Factories, mills, and other industrial sites also had waste to be disposed of. Those located on rivers often just dumped the unwanted remains into the water. Others built huge burners with chimneys to deal with the problem.

    Several facts make these choices unacceptable to modern society. The first problem is space. Dumps, which are now called landfills, are most needed in heavily populated areas. Such areas rarely have empty land suitable for this purpose. Property is either too expensive or too close to residential(住宅区的)neighborhoods. Long-distance trash hauling has been a common practice, but once farm areas are refusing to accept rubbish from elsewhere, cheap land within trucking distance of major city areas is almost nonexistent.

    Awareness of pollution dangers has resulted in more strict rules of waste disposal. Pollution of rivers, ground water, land and air is a price people can no longer pay to get rid of waste. The amount of waste, however, continues to grow.

    Recycling efforts have become commonplace, and many towns require their people to take part. Even the most efficient recycling programs, however, can hope to deal with only about 50 percent of a city's reusable waste.

    The introduction of the iPad,with its touch screen technology,has allowed even very young children to take advantage of a computer.So what if all children in a school were given an iPad to use in class and take home with them?

    Anne Laure Bazin works in a school where every child,teacher and teaching assistant is given a free iPad to use in and out of lessons.For her,the main advantage of everyone having an iPad had been the improvement in communication.Documents can be emailed straight over to workmates during a meeting.Children submit their homework by email,or through the school's learning environment.Teachers now take the register（点名）using their iPad,which means that there is a record of which children are in school,and which classroom they are in.

    The use of iPad has encouraged greater sharing of resources among teacher.All communication with parents is now done by email.Working as a group in class is much easier as children can share documents.The whole class can look at one child's work by attaching（连接）the iPad to the whiteboard.If a child has forgotten the textbook,the teacher can take a photograph of the relevant（相关的）page and send it to the student in class.

    While the use of the iPad in schools has revolutionized（变革）the way children are taught ,it hasn't completely replaced more traditional methods of teaching .Worksheets are still used in class as some children prefer the contact with paper.The children all have a textbook and exercise books.In Anne Laure's school,parents feared that the iPads would replace exercise books and children would lose handwriting skills.Anne Laure says,” The teacher are not ready to let go of the traditional style of teaching.We have welcomed the iPads in so much as they help communication and widen the resources available but we are not ready to let go of paper yet.The children themselves still value their exercise books and depend on them for review.”

    I'd planned to spend my weekend in the sun, potting flowers outdoors. But that was before the pair of crows (乌鸦). Out of nowhere, they had set up their base camp in our backyard.

    We first discovered our feathered enemies on Friday morning. It was early, and the sound the birds made traveled through our neighborhood. I figured they'd go away soon. But, no. They were getting louder and probably annoying my neighbors nearly as much as us with the noise. I admit I got a little desperate.

    Then, on Sunday afternoon, I looked out the kitchen window to see our dog Quatchi staring at something on the ground. I went to explore and found a small coal-black bird in the grass. Its eyes were milky, and it stayed perfectly still as my dog inched towards it. Only when Quatchi touched his nose to its head did it walk away. I took hold of the dog and locked him inside and came back with my camera.

    It never occurred to me that the young would be hanging out on the ground, growing and gaining strength as its parents guarded it from above. The second I saw this little creature I forgave the crows.

    To be honest, I've never been much of a bird person. I also have a healthy respect for birds, and by healthy I mean slightly fear-based. They're basically living dinosaurs.

    I wish they'd chosen another backyard. There are only so many sunny days in Seattle, and I still can't do any gardening out there. But I'm also grateful that I got to see this little bit of nature unfold up close. It's pretty amazing.

    The experience has also strengthened my desire to create a beautiful backyard garden that attracts lots of bees, butterflies, and yes, birds. They are welcome here.

    Will it matter if you don't take your breakfast? Recently a test was given in the United States. Those tested included people of different ages, from 12 to 83. During the experiment, these people were given all kinds of breakfasts, and sometimes they got no breakfast at all. Special tests were set up to see how well their bodies worked when they had eaten a certain kind of breakfast. The results show that if a person eats a proper breakfast, he or she will work with better effect than if he or she has no breakfast. This fact appears to be especially true if a person works with his brains. If a student eats fruit, eggs, bread and milk before going to school, he will learn more quickly and listen with more attention to class.

    Opposite to what many people believe, if you don't eat breakfast, you will not lose weight. This is because people become so hungry at noon that they eat too much for lunch, and end up gaining weight instead of losing. You will probably lose more weight if you reduce your other meals.

    To travel abroad, we often meet the problem of what to take and how to take it. Take as little as possible. Choose clothes for your use in different kinds of situations and when you have made your final choice, take half of it! It's always a big problem to take too many things, and anyway if necessary, you can buy what you need in America. Things like jeans, T-shirts and other clothes are good buys in the US. If you hunt around you can usually find something on sale.

    Whatever baggage you take, make sure it is easy to take. Getting on and off buses and trains, even just changing planes, can be a test if your bags are too heavy or too many. The best way is to take one holdall, like a suitcase or a backpack, and then a smaller bag. Even when you have to check in your holdall, at the airport or bus station, you can keep all your money and documents by your side. It is also a good idea to keep a change of clothing in your shoulder bag in case your suitcase or backpack gets lost by an airline or a bus company.

The means you choose to travel around the US will depend on your money, you time and something else. Since there are certain discounts available to travelers who buy their tickets outside the US, it is a good idea to make travel plans before you go. Also, when you buy your tickets outside the US, you save the eight percent sales tax. Travel is like everything else in America—you have to shop around for the best busy. Never be afraid to ask for the cheapest fare. The clerk seldom offers you the cheapest one.

    Scientists recently discovered three tyrannosaur (霸王龙) trackways in Canada. The trackways suggest the meat eaters traveled and hunted in groups. The 70-million-year- old footprints are the first tyrannosaur trackways ever found.

    Tyrannosaurs were a type of meat-eating dinosaur that included the strong Tyrannosaurus rex and Albertosaurus. “Groups of tyrannosaurs may have stuck together as a group to increase their chances of bringing down animals and individually surviving,” study coauthor Richard McCrea says. He works for Canada's Peace Region Paleontology Research Centre. It's believed that tyrannosaurs were solitary creatures. The newly discovered trackways could change the way scientists look at these frightening beasts.

    Trackways can uncover a lot about the social behavior of a species. Unfortunately, very few tyrannosaur footprints have ever been found, and until recently, the only ones known were single prints discovered in Mongolia, the western U.S., and western Canada. But in October 2011, a hunting guide named Aaron Fredlund found two tyrannosaur track marks near Tumbler Ridge, an area in the foothills of the Canadian Rockies. Over the next year, McCrea and his team searched the site and found the remaining trackways.

    The footprints are at about the same depth, which suggests the tyrannosaurs moved through the area at the same time. Impressions of the dinosaurs' rough skin are even visible in the prints. The prints are also in near-perfect condition. That's because the ground had a high clay (黏土 ) content when the dinosaurs walked through the area. The land was later covered by a thick layer of volcanic ash, which kept the marks intact (完整). "This is the most ideal situation you could ask for," McCrea says.

    Researchers aren't sure of the exact species of tyrannosaur that left the prints. But the historic findings show a great deal about how the beasts moved and behaved. “We have extremely convincing evidence that tyrannosaurs traveled in groups,” says McCrea. "This is probably the most important evidence to come out to date on that topic."