“Who needs a shopping mall if you have Taobao?" says Wang Lin, 28, a writer in Beijing. Taobao, China's largest online shopping site(网上购物网站), has become an important part of Wang Lin's life. She spends lots of money on Taobao.A growing number of Chinese Internet users like Wang have found the joys of online shopping =. Most online shoppers are students or young workers. More women shop on line than men. Clothing and home-use products（产品）are the most popular on line.
It was reported that more than 250 billion（十亿）yuan was spent on online shopping last year, 80% through Taobao.Taobao means “looking for treasure” in Chinese. People can find almost everything they need on Taobao, from clothes to books =, from candies to DVD players .
You may question the security of online shopping, Wang Lin said, "It's very safe and convenient. Unless you receive the products from the sellers and are satisfied with them, the shop owner will not get the money .You can also get your money back if you want to return the products.”
.一个周期T内在液面上方能观察到激光束的时间是( )