Alibaba started taking the lead in China, simply enough, by connecting big Chinese, manufacturers(制造商)with big buyers across the world. Its business-to-business site, Alibaba.com allowed business to buy almost everything. Alibaba's advantage wasn't hard to identify: size.

    Alibaba is just big, even by Chinese standards. Its marketplaces attract 231 million active buyers, 8 million sellers, 11.3 billion orders a year—and Alibaba is just the middleman. It encourages people to use its markets—not charging small sellers a percentage of the sale.

    If you want a quick look into the influence of Alibaba on daily Chinese life, take my experience. I moved to Beijing almost a year ago and quickly got tired of visiting small stores across the crowded, polluted city of 20 million people in search of new electronics, bathroom furnishings. “You're looking for what exactly? Why not try it? ” my Chinese teacher asked me one day. With that, my wonderful new relationship with Alibaba began.

    Alibaba's original business-to-business model now is secondary to consumer buying. Chinese retail（零售）buying makes up 80% of Alibaba's profit, and leading that group is Taobao, with 800 million items for sale and the most unbelievable selection of things you'll ever find. TMall.com is Alibaba's other big site, where you can find brand name goods from Nike and Unilever near the lowest prices.

What I have a hard time explaining to friends and family back in the U. S. is how China has gone beyond traditional shopping—big-box retailers(零售商)especially—in favor of online purchases on Taobao and a few other sites. In smaller towns than Beijing, where big retailers have not yet traveled, shopping online is shopping, and shopping is Taobao.

    I have a list of some of my recent purchases on Taobao for a sense of how extensive(广泛的) the marketplace is. Almost everything arrived a day or two after ordering with free shipping. I'm not even a big buyer, because I need friends to help me search the Chinese-language site. When I was searching my purchase history on my Chinese teacher's iPad, which helps me buy goods, I looked through with great difficulty about 10 of her purchases for every one of mine.

Amsterdam Destination Guide

    Amsterdam is one of the most popular travel destinations in the world,famous for its beautiful canals,top art museum,cycling culture,and Red Light District.It is the capital and most populous city in the Netherlands and often referred to as the "Venice of the North" because of its expansive system of bridges and canals.Here are some of the key points to remember as you plan your trip to Amsterdam.

    Must-See Attractions

    Most visitors begin their Amsterdam adventure in the Old Centre,which is full of traditional architecture, shopping centers,and coffee shops.Don't miss the Dam Square and the areas around Spui and Nieuwmarkt.The infamous Red Light District is also in this area,and definitely worth a visit to see what the type is about.You'll also want to check out Amsterdam's Museum Quarter in the South District,which is great for shopping at the Albert Cuyp Market and having a picnic in the Vondelpark.The top museums to visit are the Rijksmusuem,the Ann Frank House, and the Van Gogh Museum.

    If You Have Time

    There are several, and you should try to explore as many of them as time allows.The Canal Ring is a UNESCO World Heritage Site that was originally built to attract wealthy home owners and is a core for celebrity spotting and nightlife today.The Plantage area has most of the city's museum, including the Jewish Historical Museum, the Scheepvaart Museum,and the botanical gardens.

    Free Things to Do

    Have a picnic and bring a bottle of wine to relax and people-watch in Vondelpark Soak up some sun at one of city's beaches.

Take a walk along the canals, smell the flowers, and browse markets along the way. Hop on one of several free ferry services across the IJ River for lovely city views.

    Money Saving Tips

    Unless you really want to see the tulips blooming, avoid booking between mid-March and mid-May.This is when hotel and flight prices surge.

Look for accommodations in Amsterdam's South District,where rates are generally cheaper than in the city center.

    Buy train tickets at the machine instead of the counter to save a bit of money.

    Instead of hiring a tour guide,hop on a canal boat.They're inexpensive and will give you a unique point of view of the city.

    Check out our homepage to view price comparisons for flights,hotels,and rental cars before you book.

    Nowadays everybody seems to think that they know English. Many people speak it but few speak it really well. Practice is necessary in speaking English well.

    Reading is also one of the things that will help you to speak English better. Read whenever you can and whatever you like! Read papers and Internet sites that you like in English every day. Then, you will see that the number of known words is increasing and you are able to speak with more skills. Then you will have made the foundations and a good basis of English. It is not good to stop and get stuck there.

    Going to England or an English-speaking country is a good choice, but many people cannot afford it. If you cannot go, reading and speaking with your friends will also help you to practice your English. However, I think it is very good to visit some English-speaking country to see and test your knowledge in everyday life. You will understand the everyday usage of the language in its natural environment. There your level of English is going to improve even faster. Your ability to speak English is better. Nothing can match the excitement and happiness when a native speaker tells you that your English is very good!

    Finally, in order to speak English well, you must be persistent and do it every day. It is like playing the piano. Pianists play it every day and so should you. Include English in your life and you will see where it is going. Practice, Practice! Read, write and improve your language skills and you are on your way when you will be able to speak it with more and more confidence!

    A food additive (添加剂) is any substance that is added to food. Many people are put off by the idea of "chemicals in food." The truth is that all food is made up of chemicals. Natural substances like milk, as well as man-made ones like drinks on sale in the market, can be described by chemical formulas. Some chemical substances are indeed harmful, but a person who refused to consume any chemicals would find nothing to eat.

    The things we eat can be divided into natural and man-made substances. Some people feel that only natural foods are healthy and that all man-made ingredients are to be avoided. But many natural chemicals, found in plants and animals, are harmful when eaten, and some laboratory-made substances increase the nutritional value of food. Other chemicals have natural and man-made forms that are exactly alike: vitamin C is vitamin C, whether it comes from a test tube or from an orange. Like "chemical", "man-made" doesn't necessarily mean "not fit to eat".

    Food additives are used for many reasons. We add sugar and salt and other things to foods we prepare at home to make them taste better. Food producers have developed a range of additives that stabilize, thicken, harden, keep wet, keep firm, or improve the appearance of their products. Additives can make food more convenient or nutritious, give it a longer shelf life, and make it more attractive to the consumer, thus increasing the sales and profits of the producers.

    Food additives are presently the centre of a storm of serious argument. Food producers have been known to use additives that have not been proved safe; some substances in common use have been proved unsafe and have been taken off the market. Many people feel there's a risk of eating food to which anything has been added. But food additives are now regulated by the FDA of the federal government, and new additives will go through strict testing before they can be placed on the market. For most people, the chances of developing serious side effects (副作用) from the long-term use of presently approved (批准) food additives are very small.

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Vitamin D was recognized a century ago as the cure for rickets, a childhood disease that causes weak bones. Then, in the early 2000s, a pile of studies suggested that low vitamin D levels could be a factor in cancer, cardiovascular（心血管） disease, Parkinson's disease and so on. This simple vitamin seemed to be a cure for whatever troubled us. However, all these observational studies have a fundamental weakness: they can identify a co-occurrence between vitamin D and a disease, but they can't prove there is a cause-and-effect relation.

To look at whether taking vitamin D had curative effects, Manson and her team started the world's largest and most far-reaching randomized vitamin D trial. The study followed nearly 26,000 healthy adults, randomized to receive either 2,000 international units （IU） of vitamin D or a placebo（安慰剂）, for an average of 5.3 years. The volunteers were almost evenly split between men and women, and 20 percent of the participants were black.

The results came as a shock. Not only did vitamin D not reduce rates of cancer or heart disease, but the trial also found that vitamin D did not prevent or improve cognitive function, or reduce the risk of bone fractures（骨折）. The finding about fractures "was a real surprise to many people," Manson says.

In 2011, the Institute of Medicine established an expert committee to conduct a thorough analysis of all existing studies on vitamin D and health. The committee concluded that the bone-strengthening benefits of vitamin D remain steady when blood levels reach 12 to 16 nanograms per millililter. They also found that there were no benefits to having levels above 20ng/ml. According to measurements of vitamin D levels in the general U. S. population, most had levels of 20 ng/ml or more in 2011. Levels have actually risen since then, meaning that most people don't need to take extra vitamin D.

The ups and downs of vitamin D offer a lesson in humility. The relation between the vitamin and disease is far more complicated than it first seemed and a reminder that scientific understanding is always developing over time.