Elephants on the coast of Thailand are acting strange.They stamp their feet and motion toward the hills.The sea draws back from the beaches.Fish fall heavily in the mud.Suddenly,a huge wave appears.This is no ordinary wave.It is tsunami!

    Tsunami waves are larger and faster than normal surface waves.A tsunami wave can travel as fast as a jet plane and can be as tall as a ten-story building.Imagine dropping a stone into a pond.The water on the surface ripples（起涟漪）.A tsunami is like a very powerful ripple.Tsunamis begin when the ocean rises or falls very suddenly.Large amounts of seawater are displaced.This movement caused huge waves.

    For a tsunami to occur,there must be some kind of force that causes the ocean water to become displaced.Most tsunamis are caused by underwater earthquakes.However,volcanoes ,landslides（塌方）,large icebergs,and even meteorites（陨石）are capable of causing one of these mighty waves.

    Tsunamis are extremely powerful.Ordinary waves lose power when they break.Tsunami waves can remain powerful for several days.Because tsunami waves are so strong,they can kill people,damage property,and completely ruin an ecosystem in just one hour.

    Scientists have no way of predicting when a tsunami will hit.However,if a powerful enough earthquake occurs, scientists can send out a warning or a watch.A warning means that a tsunami will very likely hit soon.A watch means that conditions are favorable for a tsunami.When people are informed of a watch or a warning,they have more time to prepare.It is best not to get caught unaware when a tsunami is on the way.

Discovery's astronauts arrived to an exciting celebration Wednesday as nearly 700 people crowded an airplane storage place, waving flags and holding signs that read: “Welcome Home, Astronauts!”

    The seven-person team returned to Earth on Tuesday after being the first to take a space shuttle into orbit since the Columbia disaster（灾难）of 2003. 

    “In the last two and a half years, we have been through the very worst that manned space flight can bring us, and over the past two weeks we have seen the very best,” NASA Administrator Michael Griffin told the astronauts and their families and fans Wednesday. 

    The crowd waved American flags for the U.S. astronauts and Japanese flags for crew member Soichi Noguchi, one of the spacewalkers. 

    “As a rookie（新手）astronaut, I could not ask for more,” Noguchi said, “We had three spacewalks, two extra days in space and one great team.” 

    While the homecoming has been filled with excitement for what mission controllers declared a “truly spectacular test flight”, uncertainty remains for the future of the shuttle program. 

    Shortly after Discovery rose up into space July 26, a nearly 1-pound large piece of foam insulation（泡沫绝缘材料）fell from the fuel tank-the very thing that was supposed to have been fixed after Columbia exploded. The foam missed Discovery, but NASA grounded all shuttle flights until engineers fix the problem.

    NASA ground crews examined Discovery after its return from orbit and found it in good condition, an official said Wednesday at NASA‟s Dryden Flight Research Center at Edwards Air Force Base in California. 

    Technicians counted 101 dings and divots, including 20 that were larger than 1 inch. Schaaf Dean, landing support group chief, said the numbers were similar to the results of other shuttle, post-landing examinations. 

A beginning examination of the shuttle's thermal（热的）blanket showed it remained undamaged during re-en-try into the Earth's air.(Agencies)

    “Freelance retail consultant” refers to daigou in Chinese, or overseas people who buy goods for customers in the Chinese mainland.

     It's estimated that there are 40,000 daigou in Australia, most of whom are young migrants or international students looking for ways to help cover their rent and university cost.

    These freelance retail consultants have created thousands of trading routes, both small and big, into China.

    Shops in Australia sold out of instant formula （婴儿配方奶粉）, leaving many Australian parents unable to buy their preferred brands. The Sydney Morning Herald reported last year that half of Australia's infant formula sold went to China through customers selling to other customers.

    Because of this, daigou have received criticism from Australian media. The Sydney Morning Post even suggested that the Australian government should put a limit on instant formula exports.

    However, not everyone dislikes daigou. “We think daigou are good for the local economy and they are very good for our business,” Peter Nathan, the chief executive of A2 Milk, a New Zealand infant formula maker, told Reuters. “We clearly believe they are a positive force.”

    Others agree that nothing is wrong with the practice. “People are buying these products legally on the Australian market… they're not illegally being exported to China,” Tim Foulds, head of research at Euro monitor Australia and New Zealand, told The Washington Post.

    “The world feels anxious and divided, and Facebook has a lot of work to do whether it's protecting our community from abuse and hate, defending against interference by nation states, or making sure that time spent on Facebook is well spent,” Zuckerberg wrote on Facebook in January.

    If the tech firm succeeded, Facebook would end 2018 on a much better path. But the cracks in Zuckerberg's social media empire only grew as scandals(丑闻)about data misuse, security and even Facebook's leadership piled up.

    The social network has faced criticism many times since launching 14 years ago, but the public uproar reached new heights in 2018. Facebook's missteps, even as it tried to fix its problems, were yet another reminder of what happens when a company grows rapidly with little oversight(监管). They also set the stage for another showdown between the tech powerhouse and lawmakers who have their own ideas on how to manage a platform used by 2.3 billion people every month.

    “I think there's just a general growing consensus from both parties in Congress that self-policing is not going to work,” Democratic senator Mark Warner of Virginia said in an interview. Facebook pointed to a series of notes Zuckerberg published this year outlining what the tech firm has done to combat(战斗，争论)election meddling(好干预的), as well as hate speech, misinformation and other offensive content. The social network pulled down more than 1.5 billion fake accounts, launched a database of political ads and announced the creation of a Supreme Court like independent body to oversee content appals.

    But in many ways, Zuckerberg fell short of his New Year's resolution(决议). UN investigators said Facebook played a role in spreading hate speech that fueled ethnic cleansing(清洗)in Myanmar. Media outlets found loopholes(漏洞)and errors in Facebook's political ads database. Users questioned whether they should delete Facebook after learning that Cambridge Analytical, a UK political consulting firm with ties to Donald Trump's 2016 presidential campaign, gathered data on as many as 87 million Facebook users without their permission.

    In short, Facebook's problems ballooned out of the company's control.

“They created a platform where sharing was mindlessly easy and interacting with each other required almost no forethought at all,” said Woodrow Hertzog, a law and computer science professor at Northeastern University. “As a result, there was massive sharing, including leaking of personal information that put lots of people at risk.”

    I sat with my friend in a well-known coffee shop in a neighboring town of Venice. As we enjoyed our coffee, a man called the waiter and placed his order, “Two cups of coffee, one on the wall.” We got interested and observed that he was served with one cup of coffee but he paid for two. As soon as he left, the waiter attached a piece of paper to the wall saying “A Cup of Coffee.” Similar occasions took place twice while we were there. It seemed that this gesture was quite normal at this place. However, it was something unique and confusing for us.

    After a few days, when we again enjoyed coffee there, a man entered. The way this man was dressed did not match the standard or the atmosphere of this coffee shop. Poverty was evident from his looks. As he seated himself, he looked at the wall and said, “One cup of coffee from the wall.” The waiter served coffee to this man with respect and dignity. The man had his coffee and left without paying. We were amazed to watch all this when the waiter took off a piece of paper from the wall and threw it in the dustbin.

    Now it was no surprise for us; the matter was very clear. The great respect for the needy shown by people in this town moved us to tears.

    Coffee is not a necessity. However, the point is that when we take pleasure in any blessing, maybe we also need to think about those people who also appreciate that specific blessing but cannot afford.

    Note the waiter, who gets the communication going between the affording and the needy with a smile on his face. Think about the man in need: he enters the coffee shop without having to lower his self-dignity; he has a free cup of coffee without asking or knowing about who has given this cup of coffee to him; he only looked at the wall, placed an order for himself, enjoyed his coffee and left. Besides, we need to remember the role played by the wall that reflects the generosity and care of people in this town.

    Grown-ups are often surprised by how well they remember something they learned as children but have never practiced ever since. A man who has not had a chance to go swimming for years can still swim as well as ever when he gets back in the water. He can get on a bicycle after many years and still ride away. He can play, catch and hit a ball as well as his son. A mother who has not thought about the words for years can teach her daughter the poem that begins "Twinkle, twinkle, little star" or remember the story of Cinderella or Goldilocks and the Three Bears.

    One explanation is the law of overlearning, which can be stated as follows: Once we have learned something, extra learning trials (尝试) increase the length of time we will remember it.

    In childhood we usually continue to practice such skills as swimming, bicycle riding, and playing baseball long after we have learned them. We continue to listen to and remind ourselves of words such as "Twinkle, twinkle, little star" and childhood tales such as Cinderella and Goldilocks. We not only learn but overlearn.

    The multiplication tables (乘法口诀表) are an exception (例外) to the general rule that we forget rather quickly the things that we learn in school, because they are another of the things we overlearn in childhood.

The law of overlearning explains why cramming (突击学习) for an examination, though it may result in a passing grade, is not a satisfactory way to learn a college course. By cramming, a student may learn the subject well enough to get by on the examination, but he is likely soon to forget almost everything he learned. A little overlearning, on the other hand, is really necessary for one's future development.