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化学兴趣小组学生用如图所示的装置探究苯和液溴的反应并制备溴苯.

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    “It is one of the few bright spots in the Chinese economy,” says Zeng Ming. He is talking about e­commerce. Mr. Zeng, the chief strategy officer of Alibaba, a giant Chinese Internet firm, predicts that digital transactions on his firm's platforms will top 1 trillion yuan ($ 159 billion) this year—more than Amazon's and eBay's combined. That is a bold claim; but consider what happened on Singles Sunday.

      Invented a few years ago by students and seized upon by digital marketers, this festival for lonely hearts falls annually on the 11th day of the 11th month (since 1 is the loneliest number). It is like St Valentine's Day, only worse. Singletons shower each other with tender gifts: a barrage of pearls; a storm of sweets.

       This November 11th they spent a surprising 19 billion yuan on Alibaba's online platforms—a fourfold increase from a year ago, and more than double what Americans spent online last Cyber Monday (the Monday after Thanksgiving, when retailers urge Americans to shop online). About 100 million purchases were logged, accounting for 80% of the packages shipped that day. Couriers(快递员) were buried in parcels.

       So life is good for China's e­tailers, then? Not exactly. The number of digital marketers is increasing and online sales are booming. Consumers are enjoying lower prices, better service and more varieties. The problem? The pressure on profits in Chinese e­commerce is worse than that in America, reckons Elinor Leung of CLSA, a broker. “Almost no one makes money,” she says.

        The fiercest battles are being fought between online retailers and their bricks­and­mortar (传统的实体企业) rivals. Dangdang, a firm that resembles Amazon, and 360buy, another online retailer, have cut prices fiercely. Tencent, a cash­rich online giant known for its instant messaging software, is splashing out to win market share. 360buy has also just raised $ 400 million from investors to do the same. But it is unclear how much longer such firms can burn through capital.