题干

某无色溶液,由Na+、Ba2+、Al3+、AlO2、Fe3+、CO32、SO42中的若干种组成。取适量该溶液进行如下实验:①加入过量盐酸有气体生成;②在①所得溶液中再加入过量NH4HCO3溶液,有气体生成并析出白色沉淀甲;③在②所得溶液中加入过量Ba(OH)2溶液也有气体生成并产生白色沉淀乙,则原溶液中一定存在的离子是

A:Al3+、Fe3+、SO42

B:Na+、AlO2、CO32

C:Na+、Al3+、CO32、SO42

D:Na+、Ba2+、AlO2

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B

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    At one time, computers were expected largely to remove the need for paper copies of documents(文件) because they could be stored electronically. But for all the texts that are written, stored and sent electronically, a lot of them are still ending up on paper.

    It is difficult to measure the quantity of paper used as a result of use of Internet-connected computers, although just about anyone who works in an office can tell you that when e-mail is introduced, the printers start working overtime. “I feel in my bones this revolution is causing more trees to be cut down ,” says Ted Smith of the Earth Village Organization.

    Perhaps the best sign of how computer and Internet use pushes up demand for paper comes from the high-tech industry itself, which sees printing as one of its most promising new markets. Several Internet companies have been set up to help small businesses print quality documents from a computer. Earlier this week Hewlett-Packard Co. announced a plan to develop new technologies that will enable people to print even more so they can get a hard copy of a business document, a medical record or just a one-line e-mail, even if they are nowhere near a computer. As the company sees it, the more use of the Internet the greater demand for printers.

    Does all this mean environmental concerns have been forgotten? Some activists suggest people have been led to believe that a lot of dangers to the environment have gone away.

    “I guess people believe that the problem is taken care of, because of recycling,” said Kelly Quirke, director of the Rainforest Action Network in San Francisco. Yet Quirke is hopeful that high-tech may also prove helpful. He says printers that print on both sides are growing in popularity.

    The action group has also found acceptable paper made from materials other than wood, such as agricultural waste.