Many Americans buy an evergreen tree for Christmas. They put the tree in their home and hang small lights and colorful things on it. The evergreen is usually a pine or a fir tree (冷杉树). It remains green during the cold, dark months of winter in the northern part of the world. So it is a sign of everlasting life.

    Early long ago, Romans probably planted evergreen trees during a celebration in honor of their god of agriculture. The Christmas tree may have developed from a popular play performed hundreds of years ago in what is now Germany. Traditionally, the play was on December 24th, the day before Christmas. The play was about the first people that God created—Adam and Eve. People put apples on an evergreen tree to represent the tree of knowledge in the Garden of Eden.

    By the year 1600, some Germans began bringing evergreen trees into their homes. They put fruit, nuts and sweets on the trees. They gave the food to the family members and friends after the holiday season. Some people say the German religious reformer (宗教改革者) Martin Luther was the first person to add lighted candles to the tree. They say he did this to show how wonderful the stars had appeared as he travelled one night.

    In the early 1800's, German settlers in the state of Pennsylvania were the first to celebrate the holiday with Christmas trees in the United States. The Christmas tree tradition spread to many parts of the world. Today, some form of the Christmas tree is part of most Christmas celebrations.

    Chinese people are, quite rightly, proud of their food. However, when foreigners like Britons and Americans think of Chinese food, their impression of it is different to what you might think.

    Growing up in the UK, the Chinese food I was used to eating was food I now recognize as being from Guangdong. For example, a typical dish I would order would be pork in sweet and sour sauce, probably with some rice and spring rolls on the side. This is the type of food we generally eat because most Chinese immigrants(移民) to the UK have come from Guangdong. You can tell, because when most British people try to copy the sound of Chinese, they actually copy the sound of Guangdong people—hearing the real Putonghua is sometimes a shock to British people who have grown up thinking it sounds completely different!

    British attitudes to Chinese food may be changing, though. Chinese-American chef Ken Hom has been on British TV for 30 years, and he told BBC Food: "Chinese food at the beginning of the 80s (in the UK) was sweet and sour pork, mainly. Most Brits had the unchangeable view of Chinese food. Now you are seeing more local Chinese food from Sichuan, Hunan and other areas of China. It is no longer just Guangdong food." Similarly, to most Americans, Chinese food doesn't go too far past orange chicken and fortune cookies, but more Chinese local dishes are becoming successful, especially in big cities like New York.

    Attitudes have not quite changed completely, though. Many foreigners who live in China will be familiar with this question from a relative back at home: "Have they given you dog yet?" Yes, perhaps because people still know too little about Chinese culture, many people believe that Chinese people love to eat dog meat. And of course, some people do eat dogs, which to Americans is like "eating a member of one's family" according to Vision Times. Also, Chinese people eat many other things people in the West do not—chicken claws, duck heads and some animals' organs.

    But what do foreigners think when they come to China and taste real Chinese food? You'll be glad to know that in my experience, the impressions have been very good.

    While the U.S. is still debating about getting rid of the penny, Sweden is rapidly moving towards abolishing currency (货币) altogether. Though this may sound radical(过激的), it is a natural evolution in this digital society.

    Sweden, which was the first European country to introduce banknotes in 1661, has just been working harder to convince its residents that digital payments are a safer alternative to carrying cash.

    Over the years, the idea has gained popularity with residents, especially the younger generation that is much more comfortable with technology. Today many banks don't even have ATMs and some have stopped handling cash altogether!

    Tickets to ride public buses in most Swedish cities can only be purchased via cell phones. Numerous businesses are also moving towards accepting only digital payments. Even the homeless that sell street paper to make ends meet have to start accepting this mode of payment!

    But despite its growing popularity, some people don't like this radical idea. They include the homeless, elderly people as well as those living in rural areas who are still uncomfortable with mobile phones and computers. But the officials are confident that in the very near future, they will be able to convince everyone to move this safe and more cost-effective payment system.

    Sweden is not the only country trying to abolish paper currency and coins. The movement is rapidly gaining ground in Denmark and Finland as well. In 2014, Israel announced a three-step plan to go cashless and just last week the vendors(小贩)of a popular street in Sydney declared they would stop accepting currency from customers. Whether this phenomenon spreads remains to be seen. But one thing is for sure—With increasingly advanced payment systems being introduced every day, pulling out cash is rapidly becoming "uncool".

    The TED speaker series features "ideas worth spreading". With over 1,400 to choose from, we've selected a few that are perfect for students.

    ⒈Larry Smith: Why you will fail to have a great career

We humans may have an unfavorable habit of making excuses for ourselves or being too confident about ourselves. Accordingly, Larry Smith, a professor of economics at the University of Waterloo in Canada, tells us why most of us will fail to have a great career. Luckily, as he puts it, there is a way out—follow your heart, as long as it is good for your career.

    ⒉Andy Puddicombe: All it takes is 10 mindful minutes

Between dance team, volunteering and –oh, right—lectures, your life's crazy factor(因素)is about to go way up. In this entertaining and informative talk, Mindfulness, expert Andy Puddicombe teaches us how to be "more healthy, more mindful and less distracted" by taking just 10 minutes out of the day to be "more present".

    ⒊Shane Koyczan: To this day…for the bullied(欺凌)and beautiful

    This talk is sure to stay with you. Shane Koyczan's "To This Day" is an affecting spoken-word poem about bullying and being different that gained over 10 million views on YouTube. In this talk, Koyczan gives a live reading of the poem, along with some stories about his background.

    ⒋Susan Cain: The power of introverts(性格内向者)

    Does a cup of tea and a good book sound like a perfect Friday night? In this personal talk, Susan Cain argues that introverts have talents and abilities. Our culture may value being outgoing, but the world needs all kinds.